Question

A stone is tied to a string and whirled in a uniform vertical circle at a radius. Which of the following cannot be true? (Pick 2)

a) The tension in the string is greater at the bottom of the circle.
b) The gravitational force is providing the centripetal force.
c) The stone's speed is constant throughout the motion.
d) The stone experiences its miniμm speed at the top of the circle.

Answer 1

The two incorrect options are that the gravitational force is providing the centripetal force, and that the stone experiences its minimum speed at the top of the circle in vertical circular motion.

Step-by-step explanation:

When a stone is tied to a string and whirled in a uniform vertical circle, the tension in the string varies due to the combination of centripetal force and the gravitational force acting on the stone. The options that cannot be true are: b) The gravitational force is providing the centripetal force, and d) The stone experiences its minimum speed at the top of the circle. The gravitational force cannot provide the centripetal force in a vertical circle because gravity acts downwards, while centripetal force is directed towards the center of the circle at every point in the path. Additionally, at the top of the circle, if the stone moves at its slowest possible speed, it can do so because the gravitational force aids the necessary inward acceleration; thus, having the minimum speed at the top contradicts this condition, assuming the stone has constant mechanical energy throughout the motion.