A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.

AcademicPhysicsNCERTClass 9

Given:

A mass of 10 kg is at point A on a table. It is moved to point B.

To do:

To find out the work done on the object by the gravitational force if the line joining A and B is horizontal.


Solution:

Let us know a little about the work done and its formula before finding out the work done on the given object to move from A to bB horizontally from A to B by the gravitational force:

Work done:

When a force acts upon an object and the object is moved in a certain direction, it is said to be the work done by the force.


Formula for the work done:

$\boxed{W=Fd\cos\theta}$

Here, $W\rightarrow$ work done

$F\rightarrow$ Force acted upon the object

$d\rightarrow$ displacement of the object

$\theta$ Angle between the force and the displacement

Work done by the gravitational force to move the object:

It can be seen clearly in the diagram given below that a mass of $10\ kg$ is placed over a table and it is moved from point A to point B. The joining line AB is horizontal and the weight or gravitational force$(mgh)$ is vertical.

The gravitational force and displacement are perpendicular to each other. 

Therefore, the angle between the gravitational force and the displacement, $\theta=90^{\circ}$

Therefore, work done $W=Fd\cos\theta$

Or $W=mgh\times AB\times \cos90^{\circ}$

Or $W=0$                    [$\because \cos90^{\circ}=0$]

Therefore, the work done by the gravitational force is zero.

raja
Updated on 10-Oct-2022 13:22:49

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