Question

A mass of $10kg$ 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 solution

Answer 1

Diagram:

Explanation:

1. The force is acting downwards in this case.
2. Which is equal to the mass of an object multiplied by the acceleration due to gravity. $F=mg=10\times 9.81=98.1N$
3. But, according to the question, displacement from A to B is horizontal.
4. Then the angle made between force and displacement will be exactly $90°$.
5. As force and displacement are making a right angle with each other.
6. Work done is the dot product of force and displacement.
7. Now work done $\left(W\right)$= $FS\cos \theta$, where $F$=Force, $S$=Displacement, Hence $W=F\times S\times \cos 90°=0,$ As $\cos 90°=0$, whatever be the values of force and displacement,
8. Thus, the net work done will be equal to zero. or $W=0$.

Therefore, the work done on the body by gravity is zero.