# Introduction to Power

## Power

Power is the rate of doing work. Power = Work / Time. P = W/t

The unit of power is Watt (W) where 1 watt (W) = 1 J/s

Example:

A cord is used to sled a box across the ground without accelerating the sled.

The cord makes an angle to the horizontal.

Question:

Does the force applied through the cord do work on the sled?
- No, the force F does no work.
- Yes, the force F does work.
- Only part of the force F does work.
- You can't tell from this drawing.

Answer:

**
Only the part of the force that is parallel to the distance moved does work on the sled.**

This is the horizontal part of the force F.

### Exercise 1

*Exercise on Friction *

Check your answers here:
*Solution to the Friction Exercise *

### Exercise 2

*Exercise on Perpendicular Forces *

Check your answers here:
*Solution to the Perpendicular Forces *

### Exercise 3

*Exercise on Normal Forces *

Check your answers here:
*Solution to the Normal Forces *

### Exercise 4

*Exercise on Vertical Forces *

Check your answers here:
*Solution to the Vertical Forces *

### Exercise 5

*Exercise on Total Forces *

Check your answers here:
*Solution to the Total Forces *

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Date of last modification: Summer , 2019