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Unit summary

Check your knowledge and understanding

1. At a high jump competition, an athlete 4. Two students of different masses took the stairs
successfully cleared the bar. What work is done by to the 5th floor in equal periods of time. What can
gravity force: be said about the work done by each, and the
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power they generated?
а) at the start of the jump?
5. A building crane lifts 500 kg of bricks to a height
b) at maximum height?
of 10 m in 10 s.
c) during freefall?
а) Determine the work done by gravity force
while the load is being lifted.

b) Calculate the power of the lifting mechanism.

c) Find the power of a worker if he needs 5 hours
to lift all the bricks to the same height.
d) How many workers are needed to perform the
same amount of work in the same time as the
crane takes?

2. Olga Rypakova, an Olympic champion, walked
100 m in the warm-up, and later ran the same
distance. Compare the power generated by her in
the first and second scenarios.
3. Two identical cars generate different levels of
power. What can be said about their speeds?

Assess your learning

Reflect on how well you met the learning objectives of this unit. Use the worksheet provided by
your teachers to develop your own targets.

How confident am I?

I can …
explain how the magnitude of work depends on force acting on an object
explain when an object does mechanical work

calculate mechanical work
plot a force vs. displacement diagram

explain the physical meaning of power
explain what power depends on

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