# 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