Physics Worksheet

🔋 Power

Chapter: Mechanics · Level ★★☆ · Time: 30 min

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After this worksheet you can

Understand: Power DefinitionUnderstand: Units of PowerUnderstand: Power and VelocityUnderstand: Average vs. Instantaneous Power

🧠 Section A · Concept Check ● BEGINNER 4 × 1 = 4

1A machine does 3000 J of work in 15s. Find power.

2A force of 800 N moves an object at 6 m/s. Find power.

3A machine has input 2000 W and output 1600 W. Find efficiency.

4A crane lifts a 200 kg load 10m in 5s (g=10). Find the power used (Hint: find work first).

🧮 Section B · Problem Solving ● INTERMEDIATE 4 × 3 = 12

5Why is a machine's efficiency always less than 100% in the real world?

6A 100 W lightbulb runs for 5 hours. How much energy (in joules) does it use? (Hint: convert hours to seconds first)

7A motor delivers 60 W of power for 2 minutes. Find the total work done.

8If two machines do the same amount of work, but one takes half the time, how do their power outputs compare?

🚀 Section C · Challenge ● CHALLENGE 2 × 2 = 4

9A car's engine exerts 3000 N while moving at 20 m/s. Find its power output in kW.

10A machine has 90% efficiency and input power of 500 W. Find its useful output power.

💭 Reflection — the most useful thing I learned:

A ___/4 B ___/12 C ___/4 Total ___/20 Teacher's Signature Parent's Signature

✂ answer key — fold or cut before handing out

1 = 200 W 2 = 4800 W 3 = 80% 4 = W=mgh=200*10*10=20000J, P=20000/5=4000W | 5 = Some energy is always lost, typically as heat due to friction or other resistive forces 6 = 100*5*3600=1,800,000 J 7 = 60*120=7200 J 8 = The faster machine has twice the power output | 9 = 60,000 W = 60 kW 10 = 450 W