Starter quiz
- Which of these units can be used to measure energy?
- kilogram
- kilojoule ✓
- kilometre
- kilowatt
-
- Which of these is the unit of work done?
- gram
- joule ✓
- newton
- watt
-
- Which of these is the unit of force?
- joule
- kilogram
- metre
- newton ✓
-
- What is the equation for work done?
- work done = force × distance ✓
- work done = force × time
- work done = force ÷ distance
- work done = force ÷ time
-
- work done = ______ × distance
- 'force' ✓
- Put these in order of decreasing work done, starting with the greatest amount of work done.
- 1⇔A boat is pulled 5 m with a force of 21 N.
- 2⇔A 51 N load is lifted 2 m.
- 3⇔A trolley is pushed 6 m with a force of 15 N.
- 4⇔A crate is pushed 2 m with a force of 40 N.
Exit quiz
- Aisha does 6000 J of work when she runs up a hill. How much work does she do when she runs up the same hill in less time?
- less than 6000 J
- 6000 J ✓
- more than 6000 J
-
- Match the quantities to their units.
- force⇔newtons (N) ✓
- power⇔watts (W) ✓
- speed⇔metres per second (m/s) ✓
- work done⇔joules (J) ✓
- Aisha’s power when she runs up a hill is 400 W. What is her power when she runs up the same hill in less time?
- less than 400 W
- 400 W
- more than 400 W ✓
-
- Which of these is the correct equation for power?
- power = work done × distance
- power = work done ÷ distance
- power = work done × time
- power = work done ÷ time ✓
-
- What would Aisha’s power be if she walked up the hill 4× more slowly, compared to when she ran up it?
- 4× greater
- 2× greater
- the same
- 2× smaller
- 4× smaller ✓
-
- Put these in order of decreasing power, starting with the greatest amount of power.
- 1⇔80 J of work is done pushing a crate 2 m in 3 seconds.
- 2⇔100 J of work is done lifting a load 2 m in 5 seconds.
- 3⇔90 J of work is done pushing a trolley 6 m in 6 seconds.
- 4⇔100 J of work is done pulling a boat 5 m in 10 seconds.
Worksheet
Loading worksheet ...
Presentation
Loading presentation ...
Video
Lesson Details
Key learning points
- Power is equal to the rate at which work is done.
- Power is equal to the rate at which energy is transferred.
- Power = work done ÷ time.
- Power is measured in watts (W).
Common misconception
Pupils often mix up the terms power and force, which are often used interchangeably in everyday speech.
Provide opportunities for pupils to describe events in which the terms need to be used appropriately, for example in lifting two different sized weights (different forces) whilst increasing their energy at the same rate (same power).
Keywords
Work - Work is done whenever a force makes an object move. The amount of work is force multiplied by distance moved in the direction of the force.
Power - Power is the rate at which work is done.
Rate - The rate at which something changes is usually equal to the amount of change each second.
Watt (w) - The unit for measuring power is the watt (W).
Kilowatt (kw) - A thousand watts is called a kilowatt (kW).
+