Question

Analyze the explanation and identify any false statements. Each statement to be analyzed is identified by a capital letter. A bal is rotating in a horizontal plane on the end of a string of length I. (A) The rotational kinetic energy remains constant as long as the length and angular speed are fixed. (B) When the ball is pulled inward and the length of the string is shortened, the rotational kinetic energy will remain constant due to conservation of energy, (C) but the angular momentum L will not remain constant because there is an external force acting on the ball to pull it inward. (D) The moment of inertia I remains constant (E) the angular speed will remain the same throughout the process because the ball is rotating in the same plane throughout the motion.

Answer 1

Answer:

Explanation:

The rotational kinetic energy remains constant as long as the length and angular speed are fixed.

Statement A is true.

When the ball is pulled inward and the length of the string is shortened, the rotational kinetic energy will remain constant due to conservation of energy,

Statement B is false .

Reason - Conservation of energy will not be there because external work is done on the system  by the force that pulls it inward.  

but the angular momentum L will not remain constant because there is an external force acting on the ball to pull it inward

Statement C is false .

Reason - the angular momentum L will remain constant because there is an external force acting on the ball which acts perpendicular to the velocity of the ball .

The moment of inertia I remains constant

Statement D is false

Reason - because distance from axis of rotation is changing.

the angular speed will remain the same throughout the process because the ball is rotating in the same plane throughout the motion.

Statement E is false

Reason - Since moment of inertia decreases , to conserve angular momentum , angular speed increases.