Advertisements
Advertisements
प्रश्न
State the condition when the work done by a force is negative. Explain with the help of examples.
Advertisements
उत्तर
If the displacement of the body is in the direction opposite to the force, then the work done is negative.
Hence, W = - F × S
For example, when a body moves on a surface, the force of friction between the body and the surface is in a direction opposite to the motion of the body, and so the work done by the force of friction is negative.
APPEARS IN
संबंधित प्रश्न
When does a force do work?
A body of mass m is moving with a uniform velocity u. A force is applied on the body due to which its velocity changes from u to v. How much work is being done by the force?
What do you mean by uniform circular motion?
A pump is used to lift 600 kg of water from a depth of 75 m in 10s. Calculate:
- The work done by the pump,
- the power at which the pump works, and
- The power rating of the pump if its efficiency is 40%. (Take g = 10m s-2).
`["Hint" : "Efficiency" = "useful power"/"power input"]`
A man raises a box of mass 50 kg to a height of 2 m in 20s, while another man raises the same box to the same height in 50s. Calculated:
- the work done, and
- the power developed by each man. Take g = 10 N kg-1.
A boy takes 3 minutes to lift a 20 litre water bucket from a 20 m deep well, while his father does it in 2 minutes. Compare:
- the work, and
- power developed by them.
State the condition when the work done by the force is negative.
State the S.I. and C.G.S. units of energy. How are they related?
For the following scenario, state whether the work done by gravity is positive, negative, or zero.
A person climbs a ladder.
