GCSE Combined Science Energy & efficiency questions by topic

This question is about energy stores.

1. (a)Name the energy store of a moving skateboard.[1]
2. (b)Name the energy store being emptied by a falling apple.[1]
3. (c)Name the store emptied when a battery drives a torch.[1]
4. (d)Name the store that fills when you stretch an elastic band.[1]

This question is about the conservation of energy.

1. (a)State the principle of conservation of energy.[2]
2. (b)A bouncing ball never returns to its release height. Explain what happened to the missing energy.[2]

A fan heater is supplied with 1000 J of electrical energy each second. It transfers 700 J of useful thermal energy to the room.

1. (a)Calculate the heater's efficiency.[2]
2. (b)State what happens to the remaining 300 J.[1]
3. (c)Give one reason no heater can be 100% efficient.[1]

This question is about keeping buildings warm.

1. (a)Name two ways to reduce the energy lost through a house's walls.[2]
2. (b)Explain why trapping air helps insulation.[1]
3. (c)State what "thermal conductivity" tells you about a material.[1]

A 60 kg runner jogs at 4 m/s and later sprints at 8 m/s.

1. (a)Calculate the runner's kinetic energy while jogging.[2]
2. (b)Calculate the kinetic energy while sprinting.[2]
3. (c)State and explain the factor linking the two answers.[1]

A 72 kg climber rises 12 m (g = 9.8 N/kg). At a rest ledge she hangs a test weight on a spring of constant 200 N/m, stretching it 0.10 m.

1. (a)Calculate the climber's gain in gravitational potential energy.[2]
2. (b)Calculate the elastic potential energy stored in the stretched spring.[2]
3. (c)State why the two answers cannot be added to describe one single transfer.[1]

A 0.50 kg copper block (specific heat capacity 385 J/kg °C) is heated from 20 °C to 100 °C.

1. (a)Calculate the temperature change.[1]
2. (b)Calculate the thermal energy transferred to the block.[2]
3. (c)The same energy is given to 0.50 kg of water (c = 4200 J/kg °C). Explain why its temperature rise is smaller.[2]

This question is about machine power ratings.

1. (a)State what power measures.[1]
2. (b)A motor transfers 9000 J in 45 s. Calculate its power.[2]
3. (c)A 120 W lamp runs for 5.0 minutes. Calculate the energy transferred.[2]

A workshop motor is supplied with 900 J each second and delivers 540 J of useful mechanical work per second.

1. (a)Calculate the motor's efficiency and the power wasted.[3]
2. (b)Suggest two design changes that would improve the efficiency, each with a reason.[2]
3. (c)Explain why the improved motor still cannot reach 100%.[1]

This question is about measuring specific heat capacity in the lab.

1. (a)Describe how to measure the specific heat capacity of a 1.0 kg metal block.[3]
2. (b)A 50 W heater warms the block for 5.0 minutes and the temperature rises 16.5 °C. Calculate c.[2]
3. (c)The accepted value is about 900 J/kg °C. Give one reason the measured value might differ.[1]

A roller-coaster train is hauled to the top of a 20 m drop and released (mass of train and riders 500 kg, g = 9.8 N/kg). Ignore friction for parts (a)–(b).

1. (a)Calculate the train's gravitational potential energy at the top.[2]
2. (b)State its kinetic energy at the very bottom of the drop, with a reason.[2]
3. (c)In reality the train reaches the bottom with slightly less kinetic energy. Explain where the difference goes.[2]

A student claims: "A 2 kW electric fire must be twice as efficient as a 1 kW one."

1. (a)Explain the student's confusion using the definitions of power and efficiency.[2]
2. (b)The 2 kW fire delivers 1.6 kW of useful heat. Calculate its efficiency.[2]