# Physics Form 3 Exam Preparation: Questions and Answers PDF

## Physics Form 3 Questions and Answers PDF Download

Are you looking for a reliable source of Physics Form 3 questions and answers PDF download? If yes, then you have come to the right place. In this article, we will provide you with everything you need to know about Physics Form 3, including the topics covered, the exam tips, and the best way to download the PDF files for free.

## physics form 3 questions and answers pdf download

## Introduction

Physics is a fascinating subject that explores the nature of matter, energy, and their interactions. It helps us understand the world around us and the laws that govern it. Physics also has many applications in various fields such as engineering, medicine, astronomy, and technology.

Physics Form 3 is a part of the secondary school curriculum in Kenya that covers the basic principles and concepts of physics at an intermediate level. It prepares students for the national examinations at the end of Form 4, as well as for further studies in physics or related subjects.

### Why study Physics Form 3?

There are many reasons why you should study Physics Form 3, such as:

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It enhances your logical thinking and problem-solving skills.

It develops your curiosity and creativity.

It broadens your knowledge and perspective.

It opens up many opportunities for your future career or education.

### What topics are covered in Physics Form 3?

The syllabus for Physics Form 3 consists of nine topics, namely:

Applications of Vectors

Friction

Light

Optical Instruments

Thermal Expansion

Transfer of Thermal Energy

Measurement of Thermal Energy

Vapour and Humidity

Current Electricity II

Each topic covers the basic theory, the practical skills, and the relevant examples of physics in everyday life. You will also learn how to perform experiments, make observations, analyze data, and draw conclusions using physics concepts.

### How to download Physics Form 3 questions and answers PDF?

If you want to download Physics Form 3 questions and answers PDF for free, you can follow these simple steps:

Visit the website https://teacher.co.ke/physics-topical-questions/, which provides a comprehensive collection of physics questions and answers for all topics for form 1, form 2, form 3, and form 4.

Select the topic that you want to download from the list provided.

Click on the link that says "Download" or "View" to access the PDF file.

Save the file to your device or print it out for your convenience.

## Physics Form 3 Topics and Questions

### Applications of Vectors

#### Definition and examples of vectors

#### A vector is a quantity that has both magnitude (size) and direction. Examples of vectors are displacement, velocity, acceleration, force, momentum, weight, etc. A vector can be represented by an arrow that shows its direction and length (proportional to its magnitude).</p Addition and subtraction of vectors

To add or subtract vectors, we can use the triangle or parallelogram method. The triangle method involves placing the vectors head to tail and drawing the resultant vector from the tail of the first vector to the head of the last vector. The parallelogram method involves placing the vectors tail to tail and drawing the resultant vector from the common tail to the opposite corner of the parallelogram formed by the vectors.

#### Resolution and composition of vectors

To resolve a vector into two components, we can use the trigonometric ratios to find the magnitude and direction of each component. The components are usually perpendicular to each other and lie along the horizontal and vertical axes. To compose a vector from two components, we can use the Pythagoras theorem and the inverse trigonometric ratios to find the magnitude and direction of the resultant vector.

#### Sample questions and answers on vectors

Here are some sample questions and answers on vectors that you can practice with:

Question

Answer

A plane flies 200 km east and then 150 km north. What is its displacement from its starting point?

We can use the triangle method to find the displacement vector. The magnitude of the displacement is given by:

$$\\sqrt(200)^2 + (150)^2 = 250 \\text km$$

The direction of the displacement is given by:

$$\\tan^-1\\left(\\frac150200\\right) = 36.9^\\circ \\text north of east$$

Therefore, the displacement is 250 km at 36.9 north of east.

A force of 50 N acts at an angle of 30 to the horizontal. What are its horizontal and vertical components?

We can use the trigonometric ratios to find the components of the force. The horizontal component is given by:

$$50 \\cos 30^\\circ = 43.3 \\text N$$

The vertical component is given by:

$$50 \\sin 30^\\circ = 25 \\text N$$

Therefore, the horizontal component is 43.3 N and the vertical component is 25 N.

### Friction

#### Definition and types of friction

Friction is a force that opposes the relative motion or tendency to move of two surfaces in contact. There are three main types of friction, namely:

Static friction: This is the friction that acts on a stationary object when a force tries to move it. It increases as the applied force increases until it reaches a maximum value, after which the object starts to move.

Kinetic friction: This is the friction that acts on a moving object when a force tries to change its speed or direction. It is usually less than static friction and depends on the nature and speed of the surfaces.

Fluid friction: This is the friction that acts on an object when it moves through a fluid (liquid or gas). It depends on the viscosity, density, and shape of the fluid and the object.

#### Factors affecting friction

The magnitude of friction depends on two main factors, namely:

The normal force: This is the force that acts perpendicular to the surfaces in contact. It is usually equal to the weight of the object or the reaction force from a support. The greater the normal force, the greater the friction.

The coefficient of friction: This is a constant that depends on the nature and roughness of the surfaces in contact. It has no units and varies from 0 (no friction) to 1 (maximum friction). The greater the coefficient of friction, the greater the friction.

The formula for friction is given by:

#### $$F = \\mu N$$ where F is the frictional force, µ is the coefficient of friction, and N is the normal force. Advantages and disadvantages of friction

Friction has both advantages and disadvantages, depending on the situation. Some of the advantages of friction are:

It enables us to walk, run, and grip objects without slipping.

It helps us to stop, slow down, or change direction of moving objects using brakes, tyres, or gears.

It produces heat and sparks that can be used for various purposes such as welding, lighting, or cooking.

It prevents wear and tear of moving parts by providing lubrication.

Some of the disadvantages of friction are:

It opposes the motion of objects and reduces their speed and efficiency.

It causes wear and tear of moving parts and reduces their lifespan.

It produces heat and noise that can be harmful or annoying.

It wastes energy and resources that could be used for other purposes.

#### Ways of reducing friction

There are several ways of reducing friction, such as:

Using smooth or polished surfaces that have less contact area and less roughness.

Using lubricants such as oil, grease, or wax that reduce the contact between the surfaces and form a thin layer of fluid.

Using ball bearings or rollers that reduce the sliding friction to rolling friction, which is usually less.

Using streamlined shapes that reduce the drag force from the fluid friction.

#### Sample questions and answers on friction

Here are some sample questions and answers on friction that you can practice with:

Question

Answer

A car of mass 1000 kg is moving at a constant speed of 20 m/s on a horizontal road. The coefficient of kinetic friction between the tyres and the road is 0.1. What is the frictional force acting on the car?

We can use the formula for friction to find the frictional force. The normal force is equal to the weight of the car, which is given by:

$$N = mg = 1000 \\times 9.8 = 9800 \\text N$$

The frictional force is given by:

$$F = \\mu N = 0.1 \\times 9800 = 980 \\text N$$

Therefore, the frictional force acting on the car is 980 N.

A wooden block of mass 2 kg is placed on a rough table. A horizontal force of 10 N is applied to the block, but it does not move. What is the coefficient of static friction between the block and the table?

We can use the formula for friction to find the coefficient of static friction. The normal force is equal to the weight of the block, which is given by:

$$N = mg = 2 \\times 9.8 = 19.6 \\text N$$

The frictional force is equal to the applied force, which is given by:

$$F = 10 \\text N$$

The coefficient of static friction is given by:

$$\\mu = \\fracFN = \\frac1019.6 = 0.51$$

Therefore, the coefficient of static friction between the block and the table is 0.51.

### Light

#### Definition and properties of light

Light is a form of electromagnetic radiation that travels in waves and can be seen by the human eye. Light has several properties, such as:

Speed: Light travels at a constant speed of about 3 x 10^8 m/s in vacuum, but it slows down when it passes through different media.

#### Wavelength: Light has different wavelengths that correspond to different colors. The visible spectrum ranges from violet (shortest wavelength) to red (longest wavelength).Frequency: Light has different frequencies that correspond to different energies. The higher the frequency, the higher the energy.Polarization: Light can be polarized by passing through certain filters that allow only one direction of vibration to pass through.Interference: Light can interfere with each other when they meet at a point, producing constructive or destructive interference patterns.Diffraction: Light can bend around obstacles or through small openings, producing diffraction patterns.</ Reflection and refraction of light

Reflection is the bouncing back of light when it hits a smooth or shiny surface. The angle of incidence is equal to the angle of reflection, and the incident ray, the reflected ray, and the normal are all in the same plane. Examples of reflection are mirrors, water, and metals.

Refraction is the bending of light when it passes from one medium to another with a different density. The angle of refraction depends on the refractive index of the media, which is the ratio of the speed of light in vacuum to the speed of light in the medium. The higher the refractive index, the slower the light travels and the more it bends. Examples of refraction are lenses, prisms, and rainbows.

#### Critical angle and total internal reflection

The critical angle is the angle of incidence for which the angle of refraction is 90. When the angle of incidence is greater than the critical angle, no refraction occurs and all the light is reflected back into the denser medium. This phenomenon is called total internal reflection. Examples of total internal reflection are fiber optics, diamonds, and binoculars.

#### Lenses and mirrors

Lenses are transparent objects that refract light and form images of objects. There are two main types of lenses, namely:

Converging lens: This is a lens that is thicker in the middle than at the edges. It converges parallel rays of light to a point called the principal focus. It forms real or virtual images depending on the position of the object.

Diverging lens: This is a lens that is thinner in the middle than at the edges. It diverges parallel rays of light away from a point called the principal focus. It forms only virtual images that are smaller than the object.

Mirrors are reflective surfaces that reflect light and form images of objects. There are two main types of mirrors, namely:

Plane mirror: This is a flat mirror that reflects light at equal angles. It forms virtual images that are identical to the object.

Curved mirror: This is a mirror that has a curved surface that can be concave or convex. It forms real or virtual images depending on the position of the object and the type of mirror.

#### Sample questions and answers on light

Here are some sample questions and answers on light that you can practice with:

Question

Answer

An object is placed 20 cm from a converging lens of focal length 10 cm. What is the nature, position, and size of the image formed?

We can use the lens formula to find the image distance, which is given by:

$$\\frac1u + \\frac1v = \\frac1f$$

where u is the object distance, v is the image distance, and f is the focal length.

Substituting the values, we get:

$$\\frac120 + \\frac1v = \\frac110$$

Solving for v, we get:

$$v = 20 \\text cm$$

Therefore, the image distance is 20 cm.

The nature of the image is real and inverted, since v is positive and u is positive.

The magnification of the image is given by:

$$m = \\fracvu = \\frac2020 = 1$$

Therefore, the size of the image is equal to the size of the object.

A concave mirror has a radius of curvature of 40 cm. An object is placed 30 cm from the mirror. What is the nature, position, and size of the image formed?We can use the mirror formula to find the image distance, which is given by:

$$\\frac1u + \\frac1v = \\frac2R$$

where u is the object distance, v is the image distance, and R is the radius of curvature.

Substituting the values, we get:

$$\\frac130 + \\frac1v = \\frac240$$ Solving for v, we get:

$$v = -40 \\text cm$$

Therefore, the image distance is -40 cm.

The nature of the image is real and inverted, since v is negative and u is positive.

The magnification of the image is given by:

$$m = \\fracvu = \\frac-4030 = -1.33$$

Therefore, the size of the image is 1.33 times larger than the size of the object.

## Conclusion

In this article, we have covered the basics of Physics Form 3, including the topics, the exam tips, and the best way to download the questions and answers PDF for free. We hope that this article has helped you to prepare well for your Physics Form 3 exams and to improve your understanding of physics concepts. Remember to practice as much as you can and to revise regularly. We wish you all the best in your studies and exams.

## FAQs

Here are some frequently asked questions and answers about Physics Form 3:

What is the difference between scalar and vector quantities?

A scalar quantity is a quantity that has only magnitude (size) and no direction. Examples of scalar quantities are mass, speed, distance, time, etc. A vector quantity is a quantity that has both magnitude and direction. Examples of vector quantities are displacement, velocity, acceleration, force, etc.

What is the difference between concave and convex lenses?

A concave lens is a lens that is thinner in the middle than at the edges. It diverges parallel rays of light away from a point called the principal focus. It forms only virtual images that are smaller than the object. A convex lens is a lens that is thicker in the middle than at the edges. It converges parallel rays of light to a point called the principal focus. It forms real or virtual images depending on the position of the object.

What is the difference between heat and temperature?

Heat is a form of energy that flows from a hotter body to a colder body due to their temperature difference. Heat is measured in joules (J) or calories (cal). Temperature is a measure of how hot or cold a body is. Temperature is measured in degrees Celsius (C), degrees Fahrenheit (F), or kelvins (K).

What is the difference between series and parallel circuits?

A series circuit is a circuit that has only one path for the electric current to flow. The current is the same at all points in the circuit. The tota