Question

Look at the activity listed here. Reason out whether or not work is done in the light of your understanding of the term 'work'.

An engine is pulling a train.

Answer 1

Work Done

1. Work done is defined as the force applied to displace a body from its original state.
2. Work done is a scalar quantity.
3. Force and displacement are vector quantities.

1. We know that the dot product of two vectors gives a scalar quantity as its result.
2. Therefore work done is the dot product of force and displacement.

If $\overrightarrow{F}$ is the force applied and $\overrightarrow{S}$ is the displacement of the body, then the work done $W$ can be given as,

$W=\overrightarrow{F}.\overrightarrow{S}$

$=FS\cos \theta$

where, $\theta$ is the angle between the direction of force vector and displacement vector.

Check if work is done

1. An engine is a device that generates a force on the wheels.
2. The force drives the wheels to move in the forward direction.
3. So, the force applied and the displacement occur in the same direction.
4. Hence, the work is done by an engine pulling a train.