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Unit summary

Revise!

1. Is mechanical work done when: 5. What is the average power of a man if he lifts
a 10 kg bucket of water from a well that is 6 m
а) a ball is suspended on a rope?
deep in 10 s?
textbooks nis edu kz
b) an ice-skater moves across the ice?
6. An electric locomotive generates a 200 kN motive
c) a car moves at a speed of 60 km/h? force at a speed of 36 km/h. What is the work

d) a man pushes a trolley on the road? done by the electric locomotive drawing a train
for one minute?
e) a notebook and a pen are lying on a table?
3
7. A pump pumps out 300 m water from a 40 m
f) a satellite follows a circular orbit around
deep well. What amount of time is necessary for
the Earth?
this process, if the pump’s power is 20 kW?
2. A team of 6 workers completes loading work in 3
2 hours. If 2 more workers are added to the team, 8. An excavator can dig 2 m of earth with its bucket
how will this affect the total power of the team? and lift it to a height of 4 m. What is the work
How will the loading time change? done in this case? The density of the ground is
1400 kg/m .
3
3. Calculate the power of an electric motor doing
9. The height of the dam across this river is 10 m
240 kJ of work in 5 minutes.
and the power of the water flow is 2 MW.
4. A building crane does 20 kJ of work lifting a load Calculate the volume of water falling in the dam
of 2 tonnes. To what height is the load lifted? in 1 minute.

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