1. Power
Core
• Relate (without calculation) power to work done and time taken, using appropriate examples
Supplement
• Recall and use the equation P = E/t in simple systems

2. You should learn How power, work and time are related
To use the equation relating power energy (work) and time

3. WORK, ENERGY & POWER chapter 16 When a force moves an object,
energy is transferred,
and
- work is done.
In fact:
Work done =
Energy transferred

4. Force
The work done
depends on:
distance
In fact:
Work done =
Force x
distance moved

5. ? ? ? Work done = Force x distance moved joules (J) newtons (N)
metres (m)
What are the units?
The distance must be measured
in the direction of the force.

6. Example
A man lifts a brick of mass 5 kg from the floor to a shelf 2m high.
The opposing force is:
the weight of the brick. ?
Since 1 kg on Earth weighs 10 N,
then 5 kg weighs ?
50 N
Work done = Force x distance moved
= 50 N x 2 m
= 100 joules

7. Question
A man pushes a van against a friction force of 300 newtons,
for a distance of 10 m.
How much work does he do?
Work done = Force x distance moved
= 300 N x m
= joules

8. Notes More work in a shorter time means more POWER.
Power is measured in Watts (W)
P85 q2-5