In this worksheet, we will practice calculating the power required for a force to do an amount of work on an object in an amount of time.

**Q2: **

A rocket moves vertically upwards at a constant speed of 18 m/s. The weight of the rocket is 250 kN. What is the power supplied by the rocketβs engines? Give your answer in megawatts.

- A 13.9 MW
- B 45 MW
- C 44.1 MW
- D 4.5 MW
- E 2.25 MW

**Q3: **

A horse pulls a cart for 50 seconds. The work done by the force applied by the horse during this time is 37β500 J. What is the power supplied by the horse?

**Q4: **

360 W of power is supplied to do 270 J of work. How much time is taken to do this amount of work?

**Q5: **

A power of 140 W is supplied to do work for a time of 2.5 seconds. How much work is done?

**Q6: **

Which of the following formulas correctly shows the relationship between the time taken to do an amount of work and the power supplied to do the work?

- A
- B
- C
- D
- E

**Q7: **

A construction worker has to push a heavy, loaded waste container to a disposal area. This task tires the worker out and he pauses several times to rest. The distance that the container is moved in each 10-second time interval is shown in the table. Whenever the worker pushes the container, an average force of 80 N is used to push it. What is the average power supplied by the worker over the ten time intervals?

Time Interval Number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
---|---|---|---|---|---|---|---|---|---|---|

Distance (m) | 2.3 | 1.1 | 0 | 1.6 | 0.7 | 0 | 0 | 1.2 | 1.1 | 0.5 |

**Q8: **

The power supplied by a force over a 10-second time interval is shown in the graph.

How much work does the force do from = 0 s to = 2 s?

How much work does the force do from = 3 s to = 5 s?

How much work does the force do from = 2 s to = 3 s?

How much work does the force do from = 5 s to = 9 s?

**Q9: **

The work done by a force over a 10-second time interval is shown in the graph.

What instantaneous power does the force supply at = 3 s?

What instantaneous power does the force supply at = 6 s?

What average power does the force supply between = 7 s and = 9 s?

**Q10: **

Suppose that 260 J of work is done in 40 seconds. What power is required to do this amount of work?

**Q11: **

How much work is done in 600 seconds by the force from a car engine that has a power of W?