Advertisements
Advertisements
Question
State the condition when the work done by a force is negative. Explain with the help of examples.
Solution
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
RELATED QUESTIONS
When a body is placed on a table top, it exerts a force equal to its weight downwards on the table top but does not move or fall
1) Name the force exerted by the table top
2) What is the direction of the force?
A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a levelled road.
Who does more work against the force of gravity and why?
When a body moves in a circular path, how much work is done by the body? Give reason.
(Hint: The body is acted upon by the centripetal force.)
A coolie X Carrying a load on his head climbs up a slope and another coolie Y carrying the identical load on his head move the same distance on a frictionless horizontal platform. Who does more work? Explain the reason.
Name the quality which is measured in kWh.
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?
A force F when acts on a body, displace it by a distance d in a direction at an angle θ with the direction of the force. Write down the expression for the work done by the force.
State the S.I. and C.G.S. units of energy. How are they related?
A boy weighing 50 kgf climbs up from the first floor at a height of 3 m above the ground to the third floor at a height of 9 m above the ground. What will be the increase in his gravitational potential energy? (Take g = 10 N kg-1).
