WORK DONE (W)

The term "work done" refers to the transfer of energy.
→ Example:
The person transfers 50 J of energy from the chemical store in their muscles to the ball's gravitational potential energy store.

Instead, you could say,

The work done by the person to lift the ball was 50 J.

CALCULATING

W = work done in Joules (J) F = force applied in Newtons (N) → this can often also be the 'weight' of the object, especially if lifted. 

Remember: 1 kg = 10 N on Earth.

d = distance travelled in the direction of force (m).

Example 1: A person lifts an object with a mass of 15 kg up to a height of 50 cm. What work was done?

15 kg = 150 N, 50 cm = 0.5 m
150 × 0.5 = 75 J

Example 2: Two individuals push a broken car at a distance of 50 m. If they both exert 10,000 J of energy in the process, what force did they each apply?

200 ÷ 2 = 100N each

Example 3: A climber does 5000 J of work to lift himself with a force of 800 N. How high did he climb?

Power

- Power is the rate of energy transfer (or doing work).
OR
the rate at which work is done.

P = Power in watts (W) or joules per second (J/s)
t = Time in seconds (s)
W = Work done in Joules (J)

Example 1: A machine does 30 J of work in 10 seconds. How much power is that?

30 ÷ 10 = 3 W, or 3 J/s.

Example 2: What's the power rating of a toy motor that does 4200 J in 70.0 seconds?

4200 ÷ 70 = 60W