Question

When a force is exerted on an object, work is done only if the object .........? CHOICES IN THE DETAILS

A) is heavy
B) is displaced and the force is perpendicular to the displacement
C) is displaced and a component of a force is parallel to the displacement
D) remains stationary

Answer 1

`C`

Explanation:

The equation which governs the relationship between force applied `F` and displacement `s` in relation to work done `W` is,

`W=Fs cos theta` where, `theta` is the angle between `F` and `s`

So, option `A` makes no sense about this equation.

In option `B` if `theta=90^@` then `cos 90=0` so `W=0`

In option `D` if `s=0` then also `W=0`

So,as per option `C` if the force has a component along displacement i.e `F cos alpha` then ,angle between `F cos alpha` and `s` is zero,so work done = `Fcos alpha s cos 0=F cos alpha s`