Advertisements
Advertisements
Questions
The power of a motor is 40 kW. At what speed can the motor raise a load of 20,000 N?
If the power of a motor is 40 kW, calculate the speed at which it can raise the load of 20000 N.
Advertisements
Solution
Power = 40 KW
Force = 20,000 N
Power = Force × Speed
Speed = `"Power"/"Force"`
`=(40" KW")/(20,000)`
`=(40,000)/(20,000)`
= 2 m/s-1
RELATED QUESTIONS
A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.
A boy of mass 40 kg climbs up the stairs and reaches the roof at a height 8 m in 5 s. Calculate:
- the force of gravity acting on the boy,
- the work done by him against the force of gravity,
- the power spent by boy. (Take g = 10 m s-2)
State the law of conservation of energy.
Write an expression for the work done against gravity.
Mention whether work is done or not in the following activity.
| S. No | Activity | Work done or not done |
| 1. | Pushing the door | |
| 2. | Holding a doll | |
| 3. | Sitting in a bus | |
| 4. | Pushing a wall | |
| 5. | Digging soil |
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
Suma is swimming in a pond.
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A wind-mill is lifting water from a well.
