Recall everyday examples in which work is done and
power is developed
- lifting weights
- climbing stairs
- pulling a sledge
- pushing a shopping trolley.
Describe how energy is transferred when work is
done.
Work done and energy transferred are measured in joules (J). The work done on an object can be calculated if the force and distance moved are known
What does the amount of work done depends on?
- the size of the force in newtons (N)
* the distance travelled in metres (m)
What is joule (J) the unit for?
work and energy
Equation for work done
work done = force × distance
Describe power
a measurement of how quickly
work is being done
Units for power
watts (W)
What do cars have?
• have different power ratings
• have different engine sizes
which relate to fuel consumption
Equation for weight
weight = mass × gravitational field strength
Equation for power
power = work done / time
What does car fuel consumption depends on?
- the engine size, larger engines use more fuel
- the force required to work against friction
- driving style and speed - more accelerating and braking uses more fuel
- road conditions
- pressure
Drawbacks of high car fuel consumption:
- expensive for the driver
- damaging to the environment
