Question

What is the work done in holding a 20 kg weight while moving on circular path of

radius?​

Answer 1

• A body of mass 20 kg is held at a height of 2 m above the ground means there is no displacement because of which there is no change in its potential energy. Hence work done is zero.

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Answer 2

To find:

The work done in holding a 20 kg weight while moving on circular path of radius?

Calculation:

The work done by an operator can be calculated by the scalar product between the force vector and the displacement vector

Now, the force vector is equal to the weight of the body acting downwards , and the displacement vector is tangential to the circular trajectory.

Hence , the angle between force vector and displacement vector will be 90°.

$\rm \therefore \: work = \vec{F} \: . \: \vec{d}$

$\rm \implies \: work = F \times d \times \cos( \theta)$

$\rm \implies \: work = F \times d \times \cos( {90}^{ \circ} )$

$\rm \implies \: work = F \times d \times 0$

$\rm \implies \: work = 0 \: joule$

So, the work done is 0 Joules.

• A similar case is observed , when it is asked to calculate the work done by a coolie, when he lifts up the bag on his head and transports them.

• In that case also, work done comes as zero because the angle between the force and the displacement vector is 90°.