worksheet - Power, Exercises of Physics

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Power - worksheet

Combined science - Physics - Key stage 4 - Energy

Dr Fishwick

In lesson questions

Independent practice

1. Find the power of a lift that transfers 450 J of energy in 15 seconds
2. An electric motor transfers 8000 J of energy in 2.5 seconds. Calculate its power.
3. A weightlifter gives a dumbbell 6 00 J of gravitational potential energy store in 1.2 seconds. What is the weightlifter’s power?
4. What is the power of an engine that does 120 000 J of work in 2 minutes?
5. A car transfers 5.95 kJ of energy in 35 seconds. Find the power of the car. Give your answer in kW.

Independent practice

1. A ship contains an engine with a power of 24 000W. The ship’s engine runs for 12 seconds, how much energy is transferred?
2. Find the work done by an electric motor of which has a power of 125 W if it is switched on for 70s.
3. A track cyclist has a peak power of 2250 W and holds this for 10.1 s to complete a lap of the track. How much energy is transferred?
4. A motorcycle has a power of 33 kW and runs for 120 s. How much energy does it transfer?
5. A car has a power of 85 kW and runs for 15 minutes. How much energy is transferred? Give your answer in kJ.

Answers

Review

1. Define the term power. a. Power is the rate of transfer of energy.
2. Which example is a higher power? a. A sprinter running the 100 m in 10 s, or b. A marathon runner completing their last 400 m in 50 seconds Sprinter
3. Explain your answer. They are moving faster so will be transferring energy at a higher rate
4. What are the factors affecting power? The amount of energy to be transferred, time taken

Review

1. A ship contains an engine with a power of 24 000W. The ship’s engine runs for 12 seconds, how much energy is transferred? 288 000 J
2. Find the work done by an electric motor of which has a power of 125 W if it is switched on for 70s. 8750 J
3. A track cyclist has a peak power of 2250 W and holds this for 10.1 s to complete a lap of the track. How much energy is transferred? 22725 J
4. A motorcycle has a power of 33 kW and runs for 120 s. How much energy does it transfer? 3 960 000 J
5. A car has a power of 85 kW and runs for 15 minutes. How much energy is transferred? Give your answer in kJ. 76 500 kJ

Review

1. A tractor uses 187 500 J of energy to pull a plough. If the power of the tractor is 55 000 W, find the time the plough was pulled for. 3.4 s
2. How long would it take a 100 W light bulb to transfer 47 J of energy? 0.47 s
3. A crane lifts a load at power of 340 W. How long does it take for a crate to gain 1500 J of GPE? 4.4 s
4. A 2 kW hair dryer transfers 12 000 J of energy in 6 s. How much longer would it take a 1.5 kW hair dryer to transfer the same amount of energy? **2 s
5. Challenge:** How long would it take a 200 W motor to lift a 1.5 kg box to a height of 30 m? (g = 10 N/kg) (hint: think about GPE) 2.25 s