Multiple-Choice Questions
1. During energy conversion and conservation, which form of energy is released into the surroundings as waste?
a) Light b) Heat c) Sound d) Force
2. Which type of energy is stored in fossil fuels?
a) Thermal energy b) Chemical energy c) Nuclear energy d) Solar energy
3. What is the energy contained within an atom’s nucleus called?
a) Elastic energy b) Chemical energy c) Nuclear energy d) Thermal energy
4. What does one joule of work mean?
a) A force of one newton acting over one metre b) The work done when a 1 N force moves an object 1 m c) A mass of one kilogram moving one metre d) One newton per second
5. If an object moves at constant velocity and no force acts on it, how much work is done by that force?
a) Infinite b) High c) Negative d) Zero
6. What kind of physical quantity is work?
a) Vector quantity b) Scalar quantity c) Both vector and scalar d) Neither
7. If an object has no displacement, what is the work done on it by a force?
a) It increases b) It decreases c) It is zero d) It is positive
8. What is the work done when force is perpendicular to displacement (θ = 90°)?
a) FS b) −FS c) 0 d) 2FS
9. Which equation represents work?
a) W = F/S b) W = F + S c) W = F × S d) W = F − S
10. What does the area beneath a force–distance graph represent?
a) Power b) Energy c) Work d) Acceleration
11. Which is the correct formula for kinetic energy?
a) Eₖ = m·v b) Eₖ = ½·m·v c) Eₖ = ½·m·v² d) Eₖ = m·g·h
12. Which equation gives gravitational potential energy?
a) Eₚ = ½·m·v² b) Eₚ = F × S c) Eₚ = m·g·h d) Eₚ = W·h
13. Which of these types of energy can be stored?
a) Gravitational potential energy b) Chemical energy c) Elastic potential energy d) All of the above
14. According to the original paper, how is useful energy obtained from hydroelectric sources?
a) From sunlight b) From flowing water c) By burning fossil fuels d) From wind
15. A force F moves a body through distance S in the force’s direction. Which formula gives the work done?
a) W = F + S b) W = F/S c) W = F − S d) W = F × S
16. What is the energy associated with the chemicals inside an electric battery called?
a) Electrostatic energy b) Thermal energy c) Chemical potential energy d) Nuclear energy
17. What is generated when water falls from a height in a hydroelectric power station?
a) Electricity b) Heat c) Sound d) Steam
18. How do solar panels described in the paper operate?
a) They absorb solar energy and heat water b) They generate motion from wind c) They produce energy through chemical reactions d) They generate energy through atomic fission
19. In physics, when is work done?
a) When a person performs mental activity b) When a force acts on an object and moves it some distance c) When a person stands holding bricks d) When a person studies
20. If a force makes an angle θ with an object’s direction of motion, what is the work formula?
a) W = FS sin θ b) W = FS cos θ c) W = F/cos θ d) W = F + S cos θ
21. What is potential energy?
a) The capacity to do work because of motion b) The capacity to do work due to position or configuration c) The ability to apply force d) The ability to produce heat
22. Energy possessed by an object because of its position is called:
a) Kinetic energy b) Potential energy c) Chemical energy d) Solar energy
23. How can energy be transferred during events and processes?
a) Through mechanical work b) Through electrical work c) Through heat d) All of the above
24. Which statement defines work?
a) The product of force and time b) Force multiplied by distance in the direction of the force c) Mass multiplied by acceleration d) The amount of energy
25. According to energy conservation, what happens to energy?
a) It can be created and destroyed b) It cannot be created or destroyed, but can change from one form to another c) It always decreases d) It always increases
26. What type of energy does water possess when it is high above the ground at a waterfall?
a) Kinetic energy b) Potential energy c) Thermal energy d) Solar energy
27. What is exchanged when one system does work on another?
a) Mass b) Force c) Energy d) Speed
28. Why can a system not reach 100% efficiency?
a) Technology is insufficient b) Some energy loss is unavoidable c) The materials always prevent it d) It violates the laws of physics
29. Which are multiples of the unit of work?
a) Kilogram and gram b) Kilojoule and megajoule c) Newton-metre and kilonewton d) Second and minute
30. According to Einstein’s theory, what can happen to mass and energy?
a) They can be destroyed b) They can be created c) They can remain separate d) They can be converted into each other
31. Which of the following is not a renewable energy source?
a) Hydroelectric energy b) Fossil fuels c) Wind energy d) Solar energy
32. Why is a perpetual-motion machine impossible to build?
a) It is too expensive b) It would violate the laws of physics c) Losses prevent 100% efficiency d) It requires too much space
33. A water pump has a power rating of 2 kW. How much water can it raise in one minute to a height of 5 m, according to the options in the paper?
a) 1000 litres b) 1200 litres c) 2000 litres d) 2400 litres
34. Which expression is used to calculate efficiency?
a) (Useful energy output / total energy input) × 100 b) (Total energy input / useful energy output) × 100 c) (Useful power output + total power input) × 100 d) (Total power input − useful power output) × 100
35. What is the energy due to an object’s position relative to Earth’s surface called?
a) Elastic potential energy b) Chemical potential energy c) Gravitational potential energy d) Thermal energy
36. A bullet has a mass of 0.05 kg and travels at 300 m·s⁻¹. What is its kinetic energy?
a) 4500 J b) 1500 J c) 1125 J d) 2250 J
37. What are the two basic forms of mechanical energy?
a) Thermal and light energy b) Kinetic and potential energy c) Electrical and chemical energy d) Nuclear and thermal energy
38. When water falls, its potential energy is converted into which form?
a) Thermal energy b) Chemical energy c) Electrical energy d) Kinetic energy
39. What is needed to change an object’s motion?
a) Force b) Work c) Energy d) Power
40. Which formula gives power?
a) P = W × t b) P = W + t c) P = W/t d) P = E/S
41. What is the main source of solar energy?
a) The Sun b) Wind c) Water d) Fossil fuels
42. Which expression is equivalent to one joule?
a) kg·m·s⁻² b) kg·m·s⁻¹ c) kg·m²·s⁻³ d) kg·m²·s⁻²
43. If one joule of work is performed on an object, how much energy is transferred?
a) Two joules b) One joule c) Half a joule d) Ten joules
44. If a car’s speed becomes twice as large, what happens to its kinetic energy?
a) It stays the same b) It doubles c) It becomes three times as large d) It becomes four times as large
45. What is the SI unit of work?
a) Newton (N) b) Metre (m) c) Joule (J) d) Second (s)
46. How many joules are equal to 1 MJ?
a) 10² J b) 10³ J c) 10⁶ J d) 10⁻⁶ J
47. If an object’s momentum is doubled, how does its kinetic energy change for the same mass?
a) It doubles b) It becomes four times as large c) It becomes half d) It remains unchanged
48. At what angle between force and displacement is the work done greatest?
a) 0° b) 30° c) 60° d) 90°
49. During a nuclear reaction, a small loss of mass appears in which form?
a) A very small amount of energy b) A large amount of energy c) Heat only d) Light only
50. According to the options in the paper, when does a motor car run?
a) When it gets air b) When it does not receive energy from burning petrol c) When it receives energy from burning petrol d) When brakes are applied
51. What is the energy stored in a compressed or stretched spring called?
a) Gravitational potential energy b) Chemical potential energy c) Elastic potential energy d) Nuclear energy
52. What is the energy an object has because it is moving?
a) Potential energy b) Thermal energy c) Kinetic energy d) Chemical energy
53. Which statement describes renewable and non-renewable energy sources?
a) Renewables are always available, while non-renewables are limited b) Renewables are environmentally friendly in every case, while non-renewables always pollute c) Renewables are found only in some areas d) Renewables are cheap while non-renewables are expensive
54. What kind of energy is released when fossil fuels burn?
a) Chemical energy b) Thermal or internal energy c) Electrical energy d) Solar energy
55. What is the SI unit of power?
a) Joule (J) b) Newton (N) c) Watt (W) d) Second (s)
56. How many joules make up 1 kJ?
a) 10² J b) 10³ J c) 10⁶ J d) 10⁻³ J
57. What is energy?
a) The ability to apply force b) The capacity to do work c) The ability to produce motion d) The ability to generate power
58. What is power defined as?
a) Work per unit distance b) Work per unit time c) Energy per unit distance d) Energy per unit mass
Short-Answer Questions
(i) Define efficiency and write its formula(s).
(ii) Explain how power relates to work done per unit time and energy transferred per unit time.
(iii) Identify the locations in Pakistan where nuclear power stations operate.
(iv) Compare the kinetic energy of an object moving at speed v with that of an object twice its mass moving at speed ½v. Which has more kinetic energy?
(v) Explain how efficiency is used when solving energy-transfer problems.
(vi) Derive an expression for the kinetic energy of a moving object.
(vii) Define power and state its equation.
(viii) Explain how work can be found from a force–distance graph.
(ix) A man rows a boat upstream but remains stationary relative to the shore. Is work being done? Explain.
(x) Define work and explain its mathematical expression.
(xi) Explain how useful energy can be obtained from natural resources, including fossil fuels and biofuels.
(xii) Find the potential energy of a body of mass m raised through a height h.
(xiii) In Iceland, what proportion of homes use geothermal energy for heating, and how does its cost compare with oil?
(xiv) What was the main use of fossil fuels before electricity was invented?
(xv) How can energy be harnessed from wind, tides, and ocean waves?
(xvi) Describe some uses of solar energy.
(xvii) Explain how energy is transferred and stored during events and processes.
(xviii) Define work and give its SI unit.
(xix) Write a brief account of nuclear energy and geothermal energy.
(xx) A force F₁ does 5 J of work in 10 s, while force F₂ does 3 J in 5 s. Which force produces greater power?
(xxi) When a cricket ball breaks a street-side window, describe the energy transformations involved.
(xxii) Why is 100% efficiency impossible for a real system?
(xxiii) Describe the solar-powered car that won a race in Australia in 1993.
(xxiv) A car travels around a curved road at constant speed. Does its kinetic energy change? Explain.
(xxv) List the forms of energy that can be stored.
(xxvi) What was the principal use of coal up to the previous century?
(xxvii) Explain why a perpetual-motion machine cannot be made.
(xxviii) Explain the meaning of the statement: “An object has one joule of potential energy.”
(xxix) A cyclist coasts down a steep hill without pedalling and then travels up the next hill. (i) Draw a diagram of the event. (ii) Analyse what happens.
(xxx) Write the gravitational potential energy formula and explain how it is used.
(xxxi) Describe how energy is obtained from hydroelectric sources.
(xxxii) How much energy was released by the nuclear bomb dropped on Hiroshima, Japan, during World War II?
(xxxiii) How much work does the human heart perform in one heartbeat?
(xxxiv) Can an object have negative kinetic energy? Explain.
(xxxv) How can work be calculated when a force acts at an angle to the direction of motion?
(xxxvi) How does a roller coaster’s gravitational potential energy vary as it moves?
(xxxvii) What work is done on an object that remains at rest when a force is applied?
(xxxviii) Explain how a slowly moving car may have more kinetic energy than a faster motorcycle.
(xxxix) Distinguish the everyday meaning of “work” from its meaning in physics.
(xl) Define power and state its unit.
(xli) Explain how kinetic-energy and gravitational-potential-energy formulas help solve simple energy-transformation numericals.
(xlii) Define energy and explain why it is described as the capacity to do work.
(xliii) A woman climbs a staircase and gains 4500 J of gravitational potential energy. If she climbs the same stairs at twice the speed, how much potential energy will she gain?
(xliv) Is wood a renewable source of heat energy? Explain your answer.
(xlv) Why might a vehicle’s tyre burst while it is travelling on a motorway?
(xlvi) Explain how Japan, Russia, Italy, New Zealand, and the United States use geothermal energy.
(xlvii) Differentiate between renewable and non-renewable energy sources.
(xlviii) Compare renewable and non-renewable energy sources and give examples of each.
(xlix) Discuss the benefits and drawbacks of different energy-generation methods.
(l) Why are both force and displacement necessary for work to be done?
(51) State the law of conservation of energy and explain its application.
(52) Define the efficiency of a working system and explain why it cannot reach 100%.
(53) What is the annual electricity-generation capacity of a typical power plant?
Long Questions
1. A machine receives 2000 J of energy to lift an object, and 1500 J becomes useful work. Calculate the machine’s efficiency.
2. State the principle of conservation of energy and explain it with an example.
3. A pump raises 200 kg of water to a height of 10 m in 5 s. Calculate the power required.
4. A block weighing 120 N is pulled up a 20 m slope to a vertical height of 10 m by a 100 N force. Calculate the system’s efficiency.
5. A girl swings between a lowest position 1.2 m above the ground and a highest position 2.0 m above the ground. Find her maximum speed and state where it occurs.
6. Discuss the advantages and disadvantages of various energy sources.
7. A wind turbine produces 2000 W of power when wind speed is 15 m/s. Calculate the kinetic energy of the wind.
8. A car of mass 1200 kg is moving at 20 m/s. Find its kinetic energy.
9. A motor performs 5000 J of work in 10 seconds. Calculate its power.
10. Explain how hydroelectric and solar energy can be used to generate electricity.
11. A 20 kg object starts from rest. A 40 N force acts on it for 5 s. Find its kinetic energy at the end of this period.
12. An 80 N force pushes a 10 kg box up a 15 m ramp, raising it by 5 m. Calculate the efficiency of the system.
13. Define geothermal energy and explain how it can be used to generate electricity.
14. State the law of conservation of energy. Explain it using a falling object and changes in its potential and kinetic energy.
15. A force of 8 N moves an object 5 m in a straight line. If the work done is 20 J, determine the angle between the force and the direction of motion.
16. A 160 g ball is thrown vertically upward and reaches 20 m. Calculate the potential energy gained.
17. A 20 kg boy runs up a staircase 10 m high in 8 s. Calculate the power he develops.
18. A force of 600 N pushes a box 5 m in 15 s. Calculate the power.
19. Use block diagrams to show how electricity is generated from (i) hydroelectric power and (ii) fossil fuels.
20. A suitcase is pulled 20 m by a 65 N force at an angle of 30° to the direction of travel. Calculate the work done.
21. A 1000 kg car accelerates at 4 m/s² and travels 50 m in 5 s. Find the power generated by its engine.
22. Define work and derive the equation W = FS cos θ.
23. Define efficiency and derive its formula.
24. A lawn mower is pushed with a 50 N force at 45° to the horizontal and moves 20 m horizontally. Calculate the work done.
25. Calculate the work involved in (i) pushing a 5 kg box up a frictionless 10 m inclined plane at 30° to the horizontal and (ii) lifting the box vertically.
26. A car engine receives 500 W of input power and delivers 300 W of output power. Calculate its efficiency.
27. A force F acts over distance L, then increases to 2F and acts over a further distance 2L. Draw a force–displacement graph and determine the total work done.
28. A 100 W bulb operates for 5 hours. Calculate the total energy it uses in joules.
29. A 0.14 kg ball is thrown vertically upward at 35 m/s. Calculate its maximum height.
30. Explain nuclear fission and describe how nuclear energy is used to produce electricity.
31. A person does 200 J of work while pushing a box through 5 m. Calculate the applied force.
32. Describe different ways of generating energy and discuss their environmental effects.
33. A person supplies 500 J of work to push a box, but only 400 J is used to move it forward. Calculate the efficiency.
34. A truck of mass 3000 kg moves at 54 km/h. Calculate its kinetic energy.
35. Compare renewable and non-renewable energy sources and give three examples of each.
36. Name different forms of energy. Explain kinetic and potential energy with examples.
37. A ball with a mass of 180 g is thrown upward to a height of 12 m. Calculate its potential energy.
38. Explain the efficiency of a machine, how it is calculated, and why it has a limit.
39. A hydroelectric dam releases 5000 kg of water from a height of 50 m. Calculate the energy converted into electricity, assuming ideal conversion.
40. An engine raises 100 kg of water by 80 m in 25 s. Calculate the engine’s power.
41. A 20 N force pulls a box horizontally for 3 m at an angle of 60° to the horizontal. Calculate the work done.
42. A nuclear reactor generates 5 × 10¹² J of energy each second. Determine its power output.
43. Describe several renewable and non-renewable energy sources.
44. Define kinetic energy, state its unit, and explain how it is calculated.
Answer Key
b) Heat
b) Chemical energy
c) Nuclear energy
b) Work done by a force of 1 N over a distance of 1 m
d) Zero
b) Scalar quantity
c) It is zero
c) Zero
c) W=F×S
c) Work
c) Ek=21mv2
c) Ep=mgh
d) All of the above
b) From flowing water
d) W=F×S
c) Chemical potential energy
a) Electricity
a) Absorb solar energy and heat water
b) Force acts and moves the object
b) W=FScosθ
b) Energy due to position or configuration
b) Potential energy
d) All of the above
b) Force × distance in the direction of force
b) Energy cannot be created or destroyed
b) Potential energy
c) Energy
b) Unavoidable energy loss
b) Kilojoule and megajoule
d) Mass and energy can be converted into each other
b) Fossil fuels
c) Energy losses prevent 100% efficiency
c) 2000 litres
a) Useful output energy ÷ total input energy × 100
c) Gravitational potential energy
d) 2250 J
b) Kinetic and potential energy
d) Kinetic energy
c) Energy
c) P=tW
a) Sun
d) kg⋅m2⋅s−2
b) One joule
d) Four times
c) Joule
c) 106 J
b) Four times
a) 0∘
b) Large amount of energy
c) When it receives energy from burning petrol
c) Elastic potential energy
c) Kinetic energy
a) Renewable sources are replenished, while non-renewable sources are limited
b) Thermal/internal energy
c) Watt
b) 103 J
b) Capacity to do work
b) Work done per unit time