Exams › NEET › Physics

A small mass attached to a string rotates on frictionless table top as shown. If the tension in the string is increased by pulling the string causing the radius of the circular motion to decrease by a factor of 2, the kinetic energy of the mass will

1. remain constant
2. increase by a factor of 2
3. increase by a factor of 4
4. decrease by a factor of 2

Correct answer: increase by a factor of 4

Solution

The kinetic energy of the mass in circular motion is proportional to the square of the angular velocity. When the radius decreases by a factor of 2, the angular velocity increases by a factor of 2 (since angular momentum is conserved). Therefore, the kinetic energy increases by a factor of 4.

Related NEET Physics questions

• Conservation of momentum in a collision between particles can be understood from
• Assertion (A): According to Newton's third law sum of action and reaction is not equal to zero Reason (R) : The forces action and reaction acts on different bodies.
• Who proposed the concept of Inertia?
• Which of the following Newton's law(s) is/are not applicable in non-inertial reference frame.
• Assertion When a bus starts suddenly, a person standing in it falls backwards. Reason It is due to inertia of rest.
• A body of mass M hits normally a rigid wall with velocity V and bounces back with the same velocity. The impulse experienced by the body is:

⚔️ Practice NEET Physics free + battle 1v1 →