Physics System of Particles Rotational Motion JEE Main 2025 ( Rotational Motion ) MCQ (Single Correct)

A cord of negligible mass is wound around the rim of a wheel supported by spokes with negligible mass. The mass of wheel is 10 kg and radius is 10 cm and it can freely rotate without any friction. Initially the wheel is at rest. If a steady pull of 20 N is applied on the cord, the angular velocity of the wheel, after the cord is unwound by 1 m, would be:

A
B

C
D

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Text Solution

Verified by Experts
The correct answer is:
A

To determine the angular velocity of the wheel after the cord is unwound by 1 meter, we start by calculating the work done by the force

applied on the cord.
Work Done by Force (W_F):

Relationship with Kinetic Energy:
The work done (W_F) is converted into the change in kinetic energy of the wheel.
Therefore, we have:

where is the moment of inertia of the wheel, and is the angular velocity.

Determine the Moment of Inertia (I):
Since the wheel has mass and radius , and knowing it's a solid disk:

Solve for Angular Velocity :

Apply the equation for kinetic energy:

Solving for , we get:

Therefore, the angular velocity of the wheel after the cord is unwound by 1 meter is .

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