Topic 1: Introduction to Physics – Physics Form One Notes New Syllabus

Physics is the fundamental branch of science that explores the principles governing the behaviour of matter and energy in the universe. Physics deals with very large objects like planets and very small ones like atoms.

It also covers various concepts, theories and principles that provide insights into the natural world and its interactions. In this lesson, you will learn the concepts, theories and principles of Physics.

The competencies developed will enable you to apply the concepts, theories and principles of Physics to solve daily life problems. You will also be able to relate physics with other branches of natural sciences.

Concept of Physics

The universe is a totality of matter, energy, space, and time. The word universe originates from the Latin word ‘universus’ which means ‘all or everything’. It can therefore be referred to as everything surrounding us; within, near, far and beyond our planet, solar system, and galaxy in which our solar system belongs (the Milky Way Galaxy).

We are part of the universe. Science is the major tool for studying and exploring the universe. It begins with inquiries such as what is the universe? What is its origin? What makes up the universe? How does it change with time?

Why does the sky look blue? And why does iron turn red when heated? To answer such questions, the applications of theories, principles and laws of science are required.

Physics falls under a broad category of natural science, which is divided into three main branches, namely physics, chemistry, and biology. Physics is the branch of science which deals with the study of matter, energy and their interactions.

The word physics originated from the Greek word ‘Physikos’ which means ‘nature’. Physics involves the study of physical and natural phenomena around us. Examples of these phenomena are the occurrence of eclipses, causes of sunset and sunrise, the formation of the rainbow, and volcanic eruption. The Figure below shows examples of phenomena described by Physics.

Physics is the branch of science that deals with the study of matter, energy and the mutual interactions between them. A person who studies physics is known as a Physicist.

In Physics, matter is studied in relation to its motion, as well as space and time. Matter is defined as any substance which has mass and occupies space. Physics as a subject uses concepts like force, energy, and mass to explain different phenomena.

In doing so, students of physics get to learn more about matter, energy and how they interact with each other. Energy, for example, may take the form of heat, light, or electricity. Among the most important forms of energy today is electricity which can be generated in many ways including waterfalls and combustion of natural gas. Figure below shows the power generation station at Kinyerezi, Dar es Salaam.

Task 1

Identify and observe real-life examples of physics concepts in your school and home environments. Record your observations and reflect on how these examples illustrates the concept learned in class.

Physics is known to be a fundamental subject among all branches of science. The content of physics is very broad and wide in such a way that it cannot be covered within a single domain. Therefore, physics is divided into several branches, each focusing on different aspects of the universe. Some of the major branches of physics are:

Mechanics

Mechanics is the branch of physics that deals with objects that are either stationary or in motion, the influence of forces acting on them and their impacts. Under this branch, aspects like linear, circular, and oscillatory motions of objects as well as fluids and their impacts are studied.

Heat

Heat is one among the forms of energy. Heat can be transferred from one point to another by either conduction, convection or radiation. This branch of physics describes the phenomena of matter when heat energy is supplied to it.

These phenomena include the expansion of matter, changes of states of matter, and the anomalous expansion of water.

Light

Light is a form of energy that travels in a straight line. There are two types of light sources: Natural and artificial. The Sun is the primary or main source of natural light.

We see different objects with the aid of light. Our eyes enable us to see objects when light falls on them.

Electromagnetism

Electromagnetism is the branch of physics that deals with the interaction between electric and magnetic fields. It has a wide range of applications in our daily life, including generation of electricity and fabrication of motors. Life could be difficult without electricity.

Astronomy

Astronomy deals with the study of the universe (cosmos) and everything contained in it. The word astronomy originates from two Greek words, ‘astron’ which means ‘star’ and ‘nomos’ which means ‘laws’.

The Greeks referred to it as the study of laws of stars. Astronomy seeks to answer inquiries such as how celestial objects like moons, planets, stars, and galaxies originate and change with time.

Geophysics

Geophysics is the branch of physics that deals with physical processes and physical properties of the Earth and its surroundings. It speculates the interior and exterior structure of the earth in terms of physical and chemical properties.

Electronics

Electronics is the basis of modern technology. It involves the study of circuits that are made of semiconductor components like diode, transistor, and integrated circuits.

Most of communication devices are made of semiconductor materials. Examples of devices that use the principles of electronics are television, radio, Light Emitting Diode (LED) lamps, mobile phones, cameras, printers, and computers.

Physics of the atom

This is a branch of physics which deals with the behaviour of particles that make up the atom and accompanying energy. We learn about radiation which is emitted by the atom during disintegration and how we can protect ourselves from harmful radiation.

Connection between Physics and other disciplines

Physics relates to many subjects in terms of either direct applications or the principles governing the working of instruments used in a given subject. Physics is closely related to chemistry, biology and mathematics.

Physics is also related to earth sciences such as geology and meteorology. The relationships between physics and other subjects are discussed below.

Physics and chemistry

Chemistry principles are used to produce pesticides and insecticides (see Figure 1.3), perfumes, and fertilizers. Then, physics principles are applied in packaging them so that they can be released in a controlled manner from compressed cylinders or sprays.

Also, chemists use equipment designed and constructed using physics principles to achieve extraction of chemicals.

Physics and biology

A number of instruments such as microscopes used in biology are designed and constructed using physics principles. Processes such as photosynthesis, conversion of matter into energy, and even the transfer of heat used in biology can be well explained by using laws of physics.

Physics and mathematics

Mathematics is a working tool of almost all disciplines. All branches of mathematics for instance, algebra, trigonometry, and vectors are applied to study physics. More often mathematical relations are used in expressing physics concepts. For instance, force, F is directly proportional to extension, e. This concept can be expressed mathematically as;

F ∝ e

F = ke

where k is a constant of proportionality.

A graph of force, F against extension, e is shown in Figure below

Physics and meteorology

Meteorology deals with the study of weather and climate. Meteorologists use an instrument like rain gauge in Figure 1.5 (a) which is designed and constructed using the principles of physics to measure rainfall. A wind vane in Figure 1.5 (b) uses physics principles to measure direction of the wind.

Physics and astronomy

Astronomy deals with the study of objects that compose the physical universe. It involves the study of stars, planets, satellites, nebulae, galaxies as well as the distribution of matter and energy in space and time.

Due to its complexity, astronomy uses principles, theories and laws of natural science, technology, engineering and mathematics (STEM). Therefore, physics plays a crucial role in astronomy. For example, the laws of planets and other objects present in the solar system are shown in Figure below.

Task 2

Search from different resources, such as online sources, then write short notes on how physics is related with other subjects apart from natural science.

Importance of studying physics

Generally, physics helps us to understand nature. The following are examples of its importance.

(a) The study of physics enables a person to answer questions about the physical properties of matter.

(b) Physics helps to answer questions like why some materials are attracted by magnets while others are not, why the sky looks blue, and why clouds look white.

(c) The study of physics enables us to acquire skills that are required in different professions such as engineering, technology, teaching, and architecture.

(d) The study of physics enables us to acquire knowledge and skills that are applied in designing and constructing different items which are useful in our daily lives. These include simple machines such as pulleys, inclined planes, and complex ones like bicycles, escalators, and bulldozers.

(e) Physics is fun. It helps to understand the applications of physics principles in sports and games.

(f) Physics helps to understand the working principles of home appliances such as electric irons, grinders, vacuum flasks, thermos flasks, cooking stoves, televisions, and radios.

Contribution of Physics to the development of modern society

Discoveries in physics have led to various inventions that influence our lives. Electricity, motor vehicles, and electronics in general, are results of scientific and technological advancement.

The study of how to control tiny particles like electrons and protons led to the discovery of electronics which in turn led to the production of devices like calculators and computers. Other applications of physics which can be experienced in daily life situations include the following:

At home

All tools and machinery that we use in our homes to simplify work are made by applying different laws of physics. These include crowbars, hammers, door handles, cutlery, hinges, and pulleys. For example, garden shear and sprayer are used when working in a home garden as shown in Figure below

Similarly, it would be difficult to get underground water to the surface without a pulley system or water pumps. Pulleys are used for drawing water from wells by applying a small force, F shown in Figure below

Physicists have reduced the cost of electricity by applying physics principles to design and construct energy saving bulbs such as Compact Fluorescent Lamp (CFL) and Light Emitting Diodes (LED) shown in Figure below.

In hospital

Various machines are used in hospitals for the diagnosis and treatment of various diseases. These machines are designed and constructed using physics principles. Such machines include diagnostic X-ray and ultrasound machines.

The figure below shows an ultrasound machine. Handling and using these machines is based on the knowledge and skills acquired in physics. This means that those who operate these machines must know physics.

In addition, premature babies are nursed in incubators, shown in Figure below, until they attain a safe weight and physical condition for them to survive on their own. The conditions in incubators are modified to the extent that they resemble a mother’s womb to support the survival of the babies.

Syringes and needles for administering injections, feeding tubes ,and drip bottles, all apply physics principles. The figure below shows some tools used in the medical field.

Sources of energy

Some processes and machines help us to obtain energy for our daily use. These machines make use of various laws of physics to give us different forms of energy. For example, batteries, generators, and solar cells, shown in the figure below, provide electrical energy.

This energy is used in charging mobile phones, powering radios, and televisions. A car battery provides the energy needed in a car. When devices like bulbs are connected to these sources, they provide light energy for our daily use.

Transport

Application of the laws of physics such as motion and frictional forces ensure vessels used in transportation like aeroplanes, trains, ships, cars, and bicycles can move, brake and stop when necessary. The Figure below shows transport vessels that operate because the laws related to friction, flotation, and balance are observed and applied accordingly.

Remember that, if these laws are disobeyed, ships sink and trains derail. Ships and boats have refrigerators and air conditioners that function through the application of the laws of physics.

Heat is removed from the fridges by the refrigerant and prevented from entering the fridge by using insulating materials such as a rubber strip attached to the fridge door.

Communication

Communication is important to human life as it keeps us informed of day-to-day happenings. Devices used in communication systems such as radio masts, telephones, and satellite dishes shown in Figure below, antenna, and modems are used for accessing the internet, television, and radio signals using physics principles. Therefore, the knowledge of physics is essential in constructing these instruments.

Short messages (SMS) through mobile phones, electronic mail (emails), and fax messages from fax machines are also reliable means of communication. All these are the results of the application of the principles of physics. Figure below shows SMS, email, and fax from the mobile phone, computer display and fax machine.

Entertainment

Physics has enabled people to enjoy a variety of leisure activities as is evident in exercise machines (Used for walking, running or climbing while staying at the same place), bouncing castles, shown in Figure below, and other sports and electronics equipment. Inflated balloons and bouncing castles are used to entertain children.

Music and pictures are recorded on tapes or compact disks commonly referred to as CDs. They are then listened to or watched on television using a Visual Compact Disk (VCD) player, Digital Video Disk (DVD) player or USB drive. The recording process utilises physics principles. Figure below shows a DVD player and other accessories including Compact Disk.

Industry

Physics principles and laws have enabled industries to assemble, calibrate, and use highly accurate instruments. Physics can be applied in various industries such as construction, manufacturing, and automobile industries.

Many instruments used in different industries apply the laws and principles of physics in their operation. Examples of these instruments are, sawmills used for cutting wood, cranes used for lifting heavy loads, and spanners used for tightening and loosening nuts and bolts.

In schools

In schools, equipment such as computers, photocopy machines, printers, projectors, language translating devices, telescopes, cameras, and binoculars, use the knowledge of physics.

In addition, instruments and apparatus used in school laboratories are made using the knowledge and skills acquired in physics. Examples of such apparatus and instruments are shown in Figure below.

Instruments should meet certain specifications or standards that are universally accepted. This is to enable the instrument to give the same standard or common measured value when used throughout the world.

Generally, physics is applied in many fields. It is an important discipline that enables experts to determine how structures like bridges, roads, and railways should be built to ensure safety.

Activity 1

Aim

To demonstrate applications of physics.

Materials

A plane mirror, a scale balance, different masses (5 g, 10 g, 15 g), flagpole

Procedure

Part I:

1. Look at your image in a plane mirror.

2. Observe how your face looks like.

Part II:

1. Prepare a scale balance.

2. Place a 10 g mass on one side and a 15 g mass on the other side of the scale balance.

3. Record your observations.

4. Now add a 5 g mass on the side with 10 g and observe what happens.

Part III:

1. Go out of the classroom and observe the top of the flagpole.

2. Look at the full length of the string used to hoist the flag and record your observations.

Questions

(a) How did your face look like?

(b) From your observation, explain what happened in step 4.

Plane mirrors always form images of their observers. Therefore, a person looking at a mirror will see an image of himself or herself. A scale balance leans on the side that has more mass than the other.

This is useful when measuring some items such as sugar and flour. A flag is raised to the top of a flagpole using a string that is rotated on a pulley. The string is then fastened at the bottom. All of these are applications of physics in daily life.

Theories and Principles of Physics

The discipline of physics is built upon a foundation of theories and principles that have been developed and refined over centuries of scientific exploration. These theories and principles serve as the building blocks for understanding the laws and phenomena that govern the natural world.

This means scientific exploration is a very important aspect of the development of physics. Therefore, in this section, we shall discuss the aspect of scientific investigation. Further, we will discuss the existing basic theories and principles of physics.

Basic principles of scientific investigations

The basic principles of scientific investigations form the foundation of the scientific method and guide researchers in conducting systematic and reliable experiments. These principles are essential for ensuring the accuracy, objectivity, and productibility of scientific findings.

The concept of scientific investigation

The scientific method is the basic skill needed in the world of science. Humans are always curious about why and how things happen in the world. The scientific method provides scientists with a well structured platform to help find the answers to their questions.

Therefore, the scientific method is a set of steps used by scientists to investigate a problem or answer questions.

Basic steps of scientific investigation

Scientists including physicists are always looking for scientific evidence. A systematic search for evidence is recommended during and after experiments. The following are steps followed when carrying out a scientific investigation.

1. Problem identification

This is the first step in the scientific method. It is when one makes a puzzling observation.

An example of such an observation would be ‘What is the relationship between the length of the string to which the pendulum bob is attached and the time taken by the pendulum to complete a given number of oscillations?’ The following examples will help you to build competence on how to identify a problem.

Example 1

When a ball is released from the top of a ramp, it rolls down to the bottom. After several trials, you notice that the ball always stops at almost the same point. How can you identify the problem in this scenario?

Answer:

The problem in this scenario is to explain why the ball consistently stops at almost the same point on the ramp during each trial. This issue could be related to factors such as friction, air resistance, or the ramp’s incline.

Example 2

A student conducts an experiment to measure the time taken for a pendulum to complete ten oscillations. However, the results are inconsistent as the measured time varies significantly between trials. What problem can be identified in this experiment?

Answer:

The problem in this experiment is to identify the factors causing the inconsistency in the time measurements for the ten oscillations of a pendulum. Key issues in this scenario may be variations in the starting angle, air resistance, or inaccuracies in the timing method.

2. Formulating a testable hypothesis

A hypothesis is a scientific assumption or prediction of the outcome. It is a suggestion of the answer to the question asked. To formulate a testable hypothesis in physics, we must make observations on a variety of events. For example, the length of the string to which the pendulum bob is attached affects the time taken by a pendulum to complete a given number of oscillations. The following examples may help you to formulate a testable hypothesis.

Example 3

You notice that when you rub a balloon against your hair, it becomes negatively charged, and you can make small pieces of paper stick to it. What testable hypothesis can you formulate to explain this phenomenon?

Answer:

Hypothesis; If the balloon is rubbed against the hair, it will become charged and hence attract lightweight objects, like small pieces of paper, due to static electricity.

Example 1

During a solar eclipse, you observe that the temperature drops noticeably. Formulate a testable hypothesis to investigate this temperature change phenomenon.

Answer:

Hypothesis; If a solar eclipse occurs, then there will be a decrease in temperature compared to normal conditions, due to the obstruction of the sun’s radiation towards the Earth’s surface.

Task 3

You notice that some metal objects left outside during a cold night feel much colder to the touch than other objects made of wood or plastic. Propose a testable hypothesis to explain this observation.

Fact

In science we never prove a hypothesis through a single experiment because there is a chance that you made an error somewhere along the way. What you can say is that, your results support or do not support the original hypothesis.

3. Conducting an experiment

Scientists particularly physicists experiments to study the causal relationships. This is done by manipulating one or more independent variables and measuring their effects on one or more dependent variables. There are three different types of variables, namely; dependent, independent, and controlled variables.

(a) Dependent variable; A variable which changes if the experimental condition changes. For example, the dependent variable is the time it takes for the pendulum bob to complete a given number of oscillations.

(b) Independent variable; A variable which does not change even when the experimental condition is changed. For example, the length of the pendulum bob is independent variable.

(c) Controlled variable; This is a variable that is kept constant during an experiment. For example, the number of oscillations is a controlled variable.

Designing Physics experiments

Designing an experiment involves creating a set of procedures to systematically test a hypothesis. This requires a strong understanding of the system under study. For valid conclusions, the selection of a representative sample and controlling any extraneous variables is important. To experiment, we need first to understand how to identify the experimental variables. The following examples will help you to build skills on how to identify the variables that need to be manipulated.

Example 5

A student is investigating how the height of a ramp affects the distance a toy car travels. The student changes the height of the ramp and measures the distance the car travels as shown in Figure 1.19. Identify the dependent, independent, and controlled variables in this experiment.

Answer

(a) Dependent variable; The distance travelled by the toy car.

(b) Independent variable; The height of the ramp.

(c) Controlled variables; The type of toy car used, the starting point of the car on the ramp, and the surface of the ramp.

Task 4

A student is investigating the relationship between the number of coils in a spring and the distance it compresses when a force is applied. They vary the number of coils and measure the compression distance. Determine the dependent, independent, and controlled variables in this experiment.

4. Data collection and analysis

Data collection involves recording what has been observed during the experiments. The observed results are tabulated (recorded in a table form) and ready for analysis. This involves plotting graphs and calculating mean, standard deviation, and errors. The results of the experiment can be recorded as shown in Table 1.1.

Length of the string to which the pendulum bob is attached and time taken to complete number (n) of oscillations.

Activity 2

Aim: Measurement of reaction time

Material needed: stopwatch

Procedure

1. Start the stopwatch and stop after 10 seconds.

2. Repeat the procedure for 5 observations.

3. Tabulate your observations

Questions

(a) Do the observations yield the same results? Why?

(b) What should be done to improve the accuracy?

Activity 2

Aim: Measurement of reaction time

Material needed: stopwatch

Procedure

1. Start the stopwatch and stop after 10 seconds.

2. Repeat the procedure for 5 observations.

3. Tabulate your observations

Questions

(a) Do the observations yield the same results? Why?

(b) What should be done to improve the accuracy?

Measuring reaction time is an essential aspect of various scientific studies, sports performance analysis, and even everyday activities. It refers to the time it takes for a person to respond to a given stimulus. The stimulus can be visual, audio, or tactile, and the response can involve any action like pressing a button, vocalizing, or moving a body part.

5. Data presentation and interpretation

Data presentation involves the use of charts, graphs and mathematical formulae.

Drawing graphs in Physics

For all graphs plotted from experimental data, it is important to remember that you should not just connect the dots. Data do not always follow a line or curve perfectly. By obtaining several experimental data points any discrepancies in each data point can be removed. The data points plotted should be fitted by drawing the best line that describes the distribution of data points.

The graphs you plot must have the following features:

(a) The graph must have a clear descriptive title which outlines the relationship between dependent and independent variables with their appropriate units in brackets e,g A graph of temperature (°C) against time t (s).

(b) An appropriate scale is used for each axis so that the plotted points must occupy enough axis/space (work out the range of the data and the highest and lowest points). The scale must remain the same along the entire axis and should use easy intervals such as 10 s, 20 s and 50 s. Use graph paper for accuracy.

(c) Each axis must be labelled with what is shown on the axis and must include the appropriate units in brackets, e.g. Temperature (°C), time (s) and height (cm).

(d) The independent variable is generally plotted along the x-axis, while the dependent variable is generally plotted along the y-axis. Each point has an x and y co-ordinate and should be plotted with a symbol which can be easily seen, e.g., a cross or circle.

(e) A best fit line should be drawn to the graph. Do not start the graph at the origin unless there is a data point for (0,0), or if the best fit line runs through the origin.

(f) If there is more than one set of data drawn on a graph, a different symbol (and/or colour) must be used for each set and a key or legend must be included to define the symbols.

(g) Use line graphs when the relationship between the dependent and independent variables is continuous. For a line graph, you can draw a line of best fit with a ruler. Make sure the number of points are distributed fairly and evenly on each side of the line. Example of a graph of square of the period,T2(s2) against length l (m) is shown in Figure 1.20.

(h) In an exponential graph, a best fit line should be drawn by using freehand.

After recording and analysing the data, you may look for possible trends or patterns and explain why they occur that way. For instance, physicists may notice that as the length of the string to which the bob is attached increases, the time to complete a given number of oscillations also increases. This pattern forms the basis on which evidence can be obtained.

6. Drawing a conclusion

A conclusion is a summary of the result of the experiment. It includes a statement that either proves or disapproves of the hypothesis. For instance, ‘the length of the string to which the pendulum bob is attached affects the time taken by a pendulum to complete a given number of oscillations’ proves our hypothesis. The experiment may be repeated to make sure the results obtained are reliable.

Example 6

A physics student conducts an experiment to investigate the relationship between the force applied to stretch a spring and the resulting displacement. The student collects the following data:

(a) Based on the data, what conclusion can the student draw about the relationship between the force applied and the displacement of the spring?

Answer:

The data shows that there is a direct relationship between the force applied to stretch the spring and the resulting displacement. As the force applied to the spring increases, the displacement also increases proportionally. This indicates that the displacement of the spring is directly proportional to the force applied.

(b) Plot the graph of force (y-axis) against displacement (x-axis)

7. Reporting results

Scientists communicate their results to others in a final scientific report. It is very important to communicate scientific findings to the public in the form of scientific publications, at scientific conferences, in articles, TV, or radio programmes. The experimental results are presented in a specific format, so that others can read your work, understand it, and repeat the experiment.

The structure of a good scientific report includes:

(a) Aim – Brief sentence describing the purpose of the experiment;

(b) Apparatus – List of the apparatus or equipment;

(d) Results – Tables, graphs and observations about the experiment;

(e) Discussion – What your results mean; and

(f) Conclusion – Brief sentence concluding whether or not the aim was achieved.

Note: If your results do not support the hypothesis:

(i) do not leave out the experimental results;

(ii) suggest possible reasons for the difference between your hypothesis and the experimental results; and

(iii) suggest ideas for further investigations to find answer to the problem.

Task 5

Study the flow chat provided in Figure 1.22, then work on the following questions:

1. Once you formulate a research problem explain, why is it important to conduct background research before doing anything else?

2. What is the difference between a dependent, independent, and controlled variable and why is it important to identify them?

3. What is the difference between identifying a problem, a hypothesis, and a scientific theory?

4. Why is it important to repeat your experiment if the data do not fit the hypothesis?

Activity 3

In this activity, you are required to design your experiment. Use the information provided below and the scientific method flow chart shown in Figure 1.22 to design your scientific experiment. The following are basic steps to follow when designing your experiment.

1. Ask a question to which you want to find answer.

2. Write down your hypothesis.

3. Identify important variables of your investigation; those that are relevant and you can measure or observe.

4. Decide on the independent and dependent variables in your experiment and variables that must be kept constant.

5. Design the experiment that you will use to test your hypothesis:

(a) State the aim of the experiment.

(b) List all the apparatus (equipment) that will be used in your experiment.

(c) Write the method that will be used to test your hypothesis – in the correct sequence, with each step of the experiment numbered.

(d) Indicate how the results should be presented and what data are required.

Activity 4

Aim: To apply the scientific investigation method to test the accuracy of stopwatches.

Materials: Sellotape, table, pendulum bob, string, retort stand, analogue stopwatch, digital stopwatch

Procedure:

1. Arrange a simple pendulum system as shown in Figure below.

2. Pull the bob slightly to one side then release it so that it swings back and forth.

3. Using analogue stopwatch, measure the time the pendulum takes to swing back and forth.

4. Record your observation for one complete oscillation.

5. Repeat steps 3 and 4 using the digital stopwatch instead of the analogue one.

Questions

With reference to the pendulum bob, use the scientific method outlined previously to investigate whether the digital stopwatch is more accurate than the analogue stopwatch in measuring the time taken to complete one oscillation. Briefly address the following:

(a) What was the hypothesis?

(b) What kind of an experiment can be used to test the hypothesis?

(d) After comparing the measurements, which stopwatch do you think is more accurate than the other? and

(e) Write a report explaining your experiment and conclusions.

The measurement from a digital stopwatch is more accurate than the one from an analogue stopwatch. The digital stopwatch therefore, gives a more precise measurement of time than the analogue one.

Task 6

1. Discuss the steps for carrying out experiments using the scientific method.

2. Discuss the application of the scientific investigation method for a simple pendulum.

3. Briefly explain the importance of forming a hypothesis before doing an experiment.

Scientific theory

A theory in physics is a big idea or explanation that scientists come up with to describe how something in nature behaves. Think of it like a story that tries to explain why things happen the way they are observed.

For example, the theory of gravity explains why things fall down when we drop them. It says that all objects with mass are attracted to each other, and that’s why we stay on the ground and do not float on air.

Many theories explain various physical phenomena. In this section, we shall concentrate on the theory of gravity and its impact human beings.

Theory of gravity

The theory of gravity is the fundamental theory that explains the force of attraction between two objects that have mass. It says that objects with mass are attracted to each other.

The force of attraction between such objects is referred to as the force of gravity. This force is very important for our daily activities. Activity 1.4, will help you to understand the impact of the force of gravity in our daily lives. All objects on the earth are attracted toward the earth because the earth is more massive than other objects.

Significance of the theory of gravity

(i) It explains the arrangement and motion of planets, moon, and other celestial bodies in the solar system and beyond.

(ii) Helps to understand the tides and Earth’s motion around the sun.

(iii) Provide the basis for space exploration and satellite technology.

(iv) It influences our daily lives, from walking on the earth’s surface to the launching of spacecraft into space.

Laws of Physics

In physics, a law is a scientific statement that describes a physical phenomenon under certain conditions in nature. Physical laws provide important insight into the nature of the universe, and they are developed from several observations in nature.

However, physical laws do not explain the mechanism by which a phenomenon occurs. Physical laws are applicable to all objects regardless of scenario but are only meaningful within certain contexts. Examples of physics laws are the Hooks law and the law of floatation.

Hooke’s law

Hooke’s law is a law of physics that explains the force needed to extend or compress a spring by distance x. It states that “provided the elastic limit is not exceeded, the extension is directly proportional to the force applied.”

The law of floatation

The law of floatation is a crucial principle for understanding why certain objects rise or submerge in fluids. It determines whether the object will float or sink based on its density relative to the surrounding medium. The law of floatation states that ‘a floating object displaces its own weight of fluid in which it floats’

Principles of physics

In physics, a principle is a general rule or explanation of how a specific physical phenomenon occurs. Essentially, a principle is a fundamental truth that forms a foundation for explaining a physical phenomenon in nature.

In addition, principles describe some specific fundamental concepts. Developing a principle requires more explanations than the requirement for a physical law. It is for this reason; that physicists need to follow the method of scientific investigation when developing a physical principle. Examples of physics principles are Pascal’s principle, Archimede’s principle and the principle of conservation of energy.

Archimedes’ principle

Archimedes’ principle is a fundamental concept in fluid mechanics, named after Greek mathematician and scientist Archimedes. The principle explains the buoyant force experienced by an object immersed in a fluid, such as water or air.

The principle states that “Any object partially or totally immersed in a fluid experiences an upthrust which is equal to the weight of the fluid displaced by the object”. Archimedes’ principle helps to understand why objects float or sink and has a practical application in various engineering and everyday scenarios.

Pascal’s principle

Pascal’s principle accounts for the transmission of pressure in fluid. Pascal’s principle states that “When pressure is applied at any point on the surface of a fluid contained in a closed container, the pressure is transmitted undiminished to all parts of the fluid and to the walls of the container”.

The principle of conservation of energy

The principle of conservation of energy emphasises that the total energy in a system is conserved. This principle allows us to analyse complex systems, predict their behaviour, and understand how energy flows and transforms, providing a fundamental framework for understanding the physical world.

The principle states that ‘Energy can neither be created nor destroyed but it can be transformed from one form to another’.

Chapter summary

Physics is the study of the relationship between matter and energy.

People who study and work professionally in the field of physics are known as physicists.

Physicists use results from experiments to develop scientific laws that are normally expressed in the language of mathematics.

Physics is regarded as the ‘fundamental’ of natural sciences and it is related to other subjects. These subjects include chemistry, biology, and mathematics.

Physics is applied in many areas of our lives. Some of the areas where it is evident are homes, hospitals, schools, communication, transport and industry.

Physics is important since it explains the behaviour of the universe while answering many questions. It is also important in:

(a) career development;

(b) manufacturing industries; and

The scientific method is a procedure used by scientists to investigate a problem or answer questions.

The scientific investigation method is divided into several steps, namely: problem identification, asking questions, formulating a testable hypothesis, performing an experiment, data collection and analysis, data presentation, data interpretation, and drawing a conclusion.

Physics uses theories, laws, and principles to describe the universe. These includes theory of gravity, Hooke’s law, the law of floatation, Pascal’s principle and the principle of conservation of energy.

Revision Exercise

Section A

1.Choose the most correct answer

(i) How does studying physics contribute to our understanding of the natural world and the universe?

(a) Physics is not related to the study of the natural world and the universe.

(b) Physics helps us understand the behaviour of matter and energy, from subatomic particles to celestial bodies.

(d) Physics is not essential for understanding the natural world and the universe.

(ii) When a large body of experimental evidence supports the hypothesis or does not support the hypothesis, what may the hypothesis eventually be considered?

(a) an observation.

(b) an insight.

(d) a law.

(iii) Which of the following best describes a variable?

(a) A trend that shows an exponential relationship.

(b) Something whose value can change over multiple measurements.

(d) Something that remains constant over multiple measurements.

(iv) Physics is the fundamental branch of science, because the knowledge obtained in studying Physics is strongly connected to other branches of science. Which among the following statements describes how physics is connected to other disciplines like chemistry and biology?

(a) Physics studies the properties of matter and energy, which are fundamental to all sciences.

(b) Physics focuses solely on celestial bodies and space exploration.

(d) Physics has many applications in the medical field.

(v) Physics is the study of matter, energy and the interaction existing between them. What is the significance of the interaction of matter and energy in physics?

(a) It helps us understand the human body and its functions.

(b) It allows us to explore different planets and their atmospheres.

(d) It is not relevant to the study of physics.

2. Outline the fundamental components of the universe.

3. The operations of the universe lead to a lot of phenomena like motion, maintaining the shape of the earth, light, heat, and many more. The vastness of these phenomena cannot be covered within a single domain of knowledge. Describe in brief, the subfield (branches) that could cover this vast knowledge.

4. Physics is the fundamental branch of science as it provides tools for learning other disciplines. The following statements provide an insight into how physics is connected with other disciplines. Classify the statements according to the respective field and suggest the set of instruments designed using physics theories and principles to assist the working of other fields if any:

(a) exploration of the very far objects in the sky.

(b) diagnosis of disease and treatment of living organisms

(d) study of climate, weather patterns, ocean currents, and the behaviour of Earth’s crust.

(e) design and optimize technologies, structures, and system

Section B

Basic steps of scientific procedures

5. In an experiment to investigate the relationship between the angle of a ramp and the distance a toy car travels, students find that the car doesn’t move beyond a certain point for steeper angles. What is the problem that needs identification in this investigation?

6. You notice that a metal spoon left in a hot cup of tea becomes warmer to the touch, while a wooden spoon in a similar cup does not show the same change. Formulate a testable hypothesis to investigate the difference in heat transfer.

7. A group of students is studying the relationship between the mass of an object and the force required to move it across different surfaces. They change the mass of the object and measure the applied force. Identify the dependent, independent, and controlled variables in this investigation.

8. A group of students is conducting an experiment to measure the acceleration of a toy car on different inclined planes. They release the car from rest at the top of each inclined plane and measure the time it takes to reach the bottom. They collected and recorded data shown in Table

What can the students conclude about the relationship between the inclination and the time taken by the toy car to reach the bottom of the inclined plane?

Section C

Theories and principles

9. A science class is learning about the properties of materials and observes that some objects sink in water, while others float, even though they are made of the same material. Suggest and state the principle related to the above scenario.

10. During an activity in class, each student stretches a helical spring and observes its behaviour upon releasing.

(a) What behaviour did they observe

(b) What principle of Physics does the phenomenon obey?

11. A group of students are observing a plastic bottle containing water. They realize that when the bottle is punctured and squeezed, water squirts from all holes with the same pressure. Suggest and state the principle related to this observation.