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POWER
Power = Work = Energy Transferred
Time Time
Time
must be in seconds
1. A light bulb converts 500 J of
electrical energy into heat and light in
5 seconds. What is its power rating?
2. An electric kettle converts 210,000 J
of electrical energy into heat energy in 1 minute.
Calculate its power rating?
3. A person of weight 500 N climbs a 5m
flight of stairs in 100 s. Calculate the
power produced.
4. A car of mass 500 kg is driven up an
incline of vertical height 5m in 5s. Calculate
the power output of the engine.
[Gravitational field strength = 10
N/kg]
5. Calculate the energy transferred by a
300 W TV in 25 seconds.
6. Calculate the energy transferred by a
0.0002 W calculator in 5 minutes.
7. A hoist motor develops 500 W. It does
1000 J of work in lifting a mass. How
long does it take to lift the mass?
8. A car develops 44 kW. It does 1980 kJ
of work in travelling a certain
distance. How long does this take?
