# No work is done by gravity on a bowling ball resting or moving on a bowling alley because the...

## Question:

No work is done by gravity on a bowling ball resting or moving on a bowling alley because the force of gravity on the ball acts perpendicular to the surface. But on an incline, the force of gravity has a vector component parallel to the alley. Discuss the two ways this component accounts for (a) acceleration of the ball and (b) work done on the ball to change its kinetic energy.

## Normal reaction force:

The normal reaction force is perpendicular to the surface to which the object is in contact. This force is applied by the surface to the object. If there is no displacment along the direction of the normal reaction, then work done by it would be zero.

(a)

The weight is completely balanced by the normal reaction force in the case of a flat surface or bowling alley. Therefore, there is no displacement in that direction.

But in the case of the incline, the weight is not completely balanced by the normal reaction force. Only one component of the weight is balanced, which is normal to the surface, therefore the other component of the weight, which is along the incline provides the motion or net force to the object.

Hence the acceleration is produced in the ball.

(b)

Since the net force is acting on the ball, therefore acceleration will increase the velocity. Hence kinetic energy will increase.

Or we can say, the height of the object is continuously decreasing, therefore the kinetic energy will increase due to energy conservation.