Advertisements
Advertisements
Question
Avinash can run with a speed of 8 m s–1 against the frictional force of 10 N, and Kapil can move with a speed of 3 m s–1 against the frictional force of 25 N. Who is more powerful and why?
Solution
Since, Power = Force × Velocity
∴ Power of Avinash, PA = 10 N x 8 m s−1= 80 W
Power of Kapil, PK = 25 N x 3 m s−1 = 75 W
As PA > PK so, Avinash is more powerful than Kapil.
APPEARS IN
RELATED QUESTIONS
State the energy changes that occur in the following :
An electric generator (or dynamo).
Energy can exist in several forms and may change from one form to another. State the energy changes that occur in the unwinding of a watch spring.
Energy can exist in several forms and may change from one form to another. State the energy changes that occur in photosynthesis in green leaves.
State the energy changes in the following case while in use:
Burning coal
A rocket is moving up with a velocity v. If the velocity of this rocket is suddenly tripled, what will be the ratio of two kinetic energies?
Can any object have mechanical energy even if its momentum is zero? Explain.
The velocity of a body moving in a straight line is increased by applying a constant force F, for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.
A light and a heavy object have the same momentum. Find out the ratio of their kinetic energies. Which one has larger kinetic energy?
Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it.
(a) How much work is done by the men in lifting the box?
(b) How much work do they do in just holding it?
(c) Why do they get tired while holding it? (g = 10 m s–2)
For burning of coal in a thermoelectric station, the energy conversion taking place is:
