Question

A man pulls a 100 n crate up a frictionless 30° slope 5 m high as shown. assuming that the crate moves at constant speed, the work (in m·n) done by the man is:

Answer 1

Answer : Work done by the man is zero.

Explanation :

It is given that,

A man pulls a 100 n crate up a friction less 30° slope 5 m high. We know that the work done is given by :

`W=F.d`

`W=Fd\ cos\theta`

Where,

F is the applied force

d is the displacement

`\theta` is the angle between the force and the displacement

In this case, the crate moves with constant velocity. This means the acceleration of the crate is equal to zero. So, the net force will be zero.

Hence, the work done by the man is zero.

Answer 2

The work done by the man is 100 Nm. First we look at the equation for work: Work = force * distance. Since the slope is frictionless, the angle doesn’t matter. Therefore, Work = 100 * 5 = 100 Nm. (Note that a Nm is also known as a Joule.)