Physics 2000 JAMB Past Questions - Question 7: I. Its velocity is constant II. No work is done on the body. III. It has constant acceleration directed away from the centre. IV. The centripetal force is directed towards the centre. Which combination of the above is true of a body moving with constant speed in a circular track?

Correct Answer

D

Explanation

A body moving with a constant speed in a circular track exhibits the following characteristics:

I. Its velocity is constant - True. The speed (magnitude of velocity) remains constant, but the direction of velocity changes as it moves in a circle.The correct combination of statements that is true for a body moving with constant speed in a circular track is:

II. No work is done on the body.
IV. The centripetal force is directed towards the center.

Explanation:
I. Its velocity is constant - This statement is not true for a body moving in a circular track because the direction of the velocity is constantly changing, even though the speed remains constant.

II. No work is done on the body - This statement is true because work is defined as the product of force and displacement in the direction of the force. In a circular track, the force (centripetal force) is always perpendicular to the displacement, so no work is done.

III. It has constant acceleration directed away from the center - This statement is not true for a body moving in a circular track. While the body does have acceleration, it is directed towards the center of the circle, not away from it.

IV. The centripetal force is directed towards the center - This statement is true. In order to keep the body moving in a circular path, there must be a centripetal force directed towards the center of the circle. This force is responsible for changing the direction of the velocity, keeping the body in circular motion.

Therefore, the correct combination is II and IV.

II. No work is done on the body - True. When the speed is constant, there is no change in kinetic energy, and therefore no net work is done on the body.

III. It has constant acceleration directed away from the center - False. In this case, the body has a constant acceleration directed toward the center, not away from it. This inward acceleration is called centripetal acceleration.

IV. The centripetal force is directed towards the center - True. To maintain circular motion, there must be a centripetal force directed toward the center of the circle, which is responsible for keeping the body in its circular path.

So, the correct combination is:

I. Its velocity is constant
II. No work is done on the body
IV. The centripetal force is directed towards the center