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O Level Physics Energy Power Quiz

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Questions

O-Level Physics Quiz - Energy Power

Name: __________________________
Class: __________________________
Date: __________________________
Score: _______ / 50

Duration: 45 minutes
Total Marks: 50

Instructions:

Answer all questions.
Write your answers in the spaces provided.
Show all working clearly. Marks are awarded for correct method and steps.
Use $g = 10 \text{ m/s}^2$ where necessary.

Section A: Multiple Choice & Short Concepts (Questions 1–5)

[10 Marks]

1. Which of the following is a unit of power?
A. Joule (J)
B. Newton (N)
C. Watt (W)
D. Pascal (Pa)

Answer: ____________________ [1]

2. A ball is dropped from a height. As it falls, air resistance is negligible. Which energy transformation takes place?
A. Kinetic energy to gravitational potential energy
B. Gravitational potential energy to kinetic energy
C. Chemical energy to kinetic energy
D. Elastic potential energy to gravitational potential energy

Answer: ____________________ [1]

3. State the Principle of Conservation of Energy.

_________________________________________________________________________ [2]

4. Define power in terms of energy and time.

_________________________________________________________________________ [1]

5. A machine has an efficiency of 80%. If the total energy input is 500 J, calculate the useful energy output.

Useful Energy Output = ____________________ J [2]

Section B: Structured Calculations (Questions 6–12)

[25 Marks]

6. A crane lifts a load of mass 200 kg vertically through a height of 15 m in 30 seconds.
(a) Calculate the weight of the load.

Weight = ____________________ N [1]

(b) Calculate the work done by the crane in lifting the load.

Work Done = ____________________ J [2]

Power = ____________________ W [2]

7. A car of mass 1200 kg is traveling at a speed of 20 m/s.
(a) Calculate the kinetic energy of the car.

Kinetic Energy = ____________________ J [2]

(b) The driver applies the brakes, and the car comes to a stop. State what happens to the kinetic energy of the car.

_________________________________________________________________________ [1]

8. An electric motor lifts a box. The motor consumes 10,000 J of electrical energy. The box gains 8,000 J of gravitational potential energy.
(a) Calculate the efficiency of the motor.

Efficiency = ____________________ % [2]

(b) State one form of wasted energy produced by the motor.
_________________________________________________________________________ [1]

9. A student pushes a box across a horizontal floor with a constant force of 50 N. The box moves a distance of 4 m in the direction of the force.
(a) Calculate the work done by the student.

Work Done = ____________________ J [2]

(b) If the student pushes the box for 8 seconds, calculate the power exerted by the student.

Power = ____________________ W [2]

10. A hydroelectric power station uses water falling from a height of 50 m to generate electricity.
(a) Calculate the gravitational potential energy lost by 1 kg of water falling 50 m.

GPE lost = ____________________ J [2]

(b) If the water flows at a rate of 1000 kg per second, calculate the maximum theoretical power available from the falling water.

Power = ____________________ W [2]

11. A spring is extended by 0.2 m when a force of 10 N is applied. Assume the limit of proportionality is not exceeded.
(a) Calculate the elastic potential energy stored in the spring.
(Hint: Work done = average force × extension, or use $E_e = \frac{1}{2}Fx$ )

Elastic PE = ____________________ J [2]

(b) State the energy transformation when the spring is released and returns to its original length.
_________________________________________________________________________ [1]

12. A renewable energy source is defined as one that will not run out.
(a) Name two renewable energy sources.

__________________________ [2]

(b) State one advantage of using solar energy over fossil fuels.
_________________________________________________________________________ [1]

Section C: Application & Reasoning (Questions 13–20)

[15 Marks]

13. Explain why the efficiency of any machine is always less than 100%.

_________________________________________________________________________ [2]

14. A pendulum bob is pulled to one side and released. Describe the energy changes as it swings from the highest point on one side to the lowest point in the middle.

_________________________________________________________________________ [2]

15. Two students, A and B, run up the same flight of stairs. Student A takes 10 seconds, and Student B takes 15 seconds. They have the same mass.
(a) Who does more work against gravity? Explain your answer.

_________________________________________________________________________ [2]

(b) Who develops more power? Explain your answer.

_________________________________________________________________________ [2]

16. A light bulb is rated at 60 W.
(a) What does the rating "60 W" mean?
_________________________________________________________________________ [1]

(b) Calculate the energy transferred by the bulb if it is switched on for 5 minutes.

Energy = ____________________ J [2]

17. In a coal-fired power station, chemical energy in coal is converted to electrical energy.
List the sequence of energy transformations that occur in the power station.

_________________________________________________________________________ [2]

18. A roller coaster car starts from rest at the top of a hill (Point A) and travels down to the bottom (Point B).
(a) At which point (A or B) is the kinetic energy maximum?
__________________________ [1]

(b) At which point (A or B) is the gravitational potential energy maximum?
__________________________ [1]

19. Why is nuclear energy considered a non-renewable energy source, even though it does not produce carbon dioxide emissions?

_________________________________________________________________________ [1]

20. A force of 100 N is applied to a block, but the block does not move.
Calculate the work done by this force.

Work Done = ____________________ J [1]

*** End of Quiz ***

Answers

O-Level Physics Quiz - Energy Power (Answer Key)

Total Marks: 50

Section A: Multiple Choice & Short Concepts

1. C
[1 mark]

2. B
[1 mark]

3. Energy cannot be created or destroyed; it can only be transformed from one form to another (or transferred from one store to another).
[2 marks: 1 for "cannot be created/destroyed", 1 for "transformed/transferred"]

4. Power is the rate of energy transfer (or work done per unit time).
[1 mark]

5. $\text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} \times 100\%$ $80\% = \frac{\text{Useful Output}}{500} \times 100\%$ $\text{Useful Output} = 0.80 \times 500 = 400 \text{ J}$ [2 marks: 1 for substitution/method, 1 for answer]

Section B: Structured Calculations

6.
(a) $W = mg = 200 \times 10 = 2000 \text{ N}$
[1 mark]

(b) $\text{Work Done} = \text{Force} \times \text{Distance} = 2000 \times 15 = 30,000 \text{ J}$
[2 marks: 1 for formula/sub, 1 for answer]

(c) $\text{Power} = \frac{\text{Energy}}{\text{Time}} = \frac{30,000}{30} = 1000 \text{ W}$
[2 marks: 1 for formula/sub, 1 for answer]

7.
(a) $E_k = \frac{1}{2}mv^2 = \frac{1}{2} \times 1200 \times (20)^2$
$E_k = 600 \times 400 = 240,000 \text{ J}$
[2 marks: 1 for formula/sub, 1 for answer]

(b) The kinetic energy is transformed into thermal energy (heat) and sound energy due to friction in the brakes and air resistance.
[1 mark]

8.
(a) $\text{Efficiency} = \frac{8000}{10000} \times 100\% = 80\%$
[2 marks: 1 for calculation, 1 for answer]

(b) Thermal energy (or heat) / Sound energy.
[1 mark]

9.
(a) $\text{Work Done} = F \times d = 50 \times 4 = 200 \text{ J}$
[2 marks]

(b) $\text{Power} = \frac{\text{Work}}{\text{Time}} = \frac{200}{8} = 25 \text{ W}$
[2 marks]

10.
(a) $\text{GPE} = mgh = 1 \times 10 \times 50 = 500 \text{ J}$
[2 marks]

(b) $\text{Power} = \frac{\text{Energy}}{\text{Time}}$ . Since mass flow is 1000 kg/s, Energy per second = $1000 \times 500 \text{ J} = 500,000 \text{ J/s}$ .
$\text{Power} = 500,000 \text{ W}$ (or 500 kW).
[2 marks: 1 for logic/calc, 1 for answer]

11.
(a) $E_e = \frac{1}{2}Fx = \frac{1}{2} \times 10 \times 0.2 = 1.0 \text{ J}$
[2 marks]

(b) Elastic potential energy transforms into kinetic energy.
[1 mark]

12.
(a) Any two from: Solar, Wind, Hydroelectric, Geothermal, Biomass, Tidal.
[2 marks]

(b) Any one from: Does not produce greenhouse gases / Renewable / Lower running costs.
[1 mark]

Section C: Application & Reasoning

13. Because some energy is always wasted (dissipated) as heat or sound due to friction or air resistance in the moving parts. Therefore, useful output energy is always less than total input energy.
[2 marks]

14. Gravitational potential energy decreases and is transformed into kinetic energy. At the lowest point, GPE is minimum and Kinetic Energy is maximum.
[2 marks]

15.
(a) Both do the same amount of work. Work done against gravity depends on weight and vertical height ( $W=mgh$ ). Since mass and height are the same, work is the same.
[2 marks]

(b) Student A develops more power. Power is work done divided by time ( $P=W/t$ ). Since Student A takes less time to do the same work, their power is higher.
[2 marks]

16.
(a) It means the bulb transfers 60 Joules of electrical energy per second.
[1 mark]

(b) $t = 5 \text{ mins} = 300 \text{ s}$ .
$E = P \times t = 60 \times 300 = 18,000 \text{ J}$ .
[2 marks]

17. Chemical Energy $\rightarrow$ Thermal (Heat) Energy $\rightarrow$ Kinetic Energy (of steam/turbine) $\rightarrow$ Electrical Energy.
[2 marks: deduct 1 if sequence is wrong]

18.
(a) Point B
[1 mark]

(b) Point A
[1 mark]

19. Because the fuel source (uranium) is finite and will eventually run out; it cannot be replenished on a human timescale.
[1 mark]

20. $\text{Work Done} = \text{Force} \times \text{Distance moved in direction of force}$ . Since distance is 0, Work Done = 0 J.
[1 mark]