A crane raises a 500 kg steel beam up a building 50 m tall. Take the gravitational field strength as 10 N/kg.
02[1 mark]
Work out the energy the beam gains from being lifted, in J.
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2500 joules
5000 joules
25 000 joules
250 000 joules
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The energy gained is found from:. energy gained = mass × field strength × height. Multiplying the three:. 500 × 10 = 5000. 5000 × 50 = 250 000 J. That is the last option. 2500 joules comes from dividing the mass by 10 first, which is not the rule. 5000 joules leaves out the height. 25 000 joules leaves out the field strength.
1 mark
How the marks are earned
- Choose 250 000 joules: the energy gained is the beam's mass, times the field strength, times the height it rises, so 500 kg at 10 N/kg lifted 50 m gives 250 000 joules.
- The right option alone earns the mark with no working needed. One answer only: two answers earn nothing, and a circled or underlined right option counts if the box is blank.