A uniform disc of mass 2kg and radius 1m is mounted on an a…

Physics System of Particles Rotational Motion Mix MCQ (Single Correct)

A uniform disc of mass 2kg and radius 1m is mounted on an axle supported on fixed frictionless bearings. A light chord is wrapped around the rim of the disc and mass of 1kg is tied to the free end. If it is released from rest-

The tension in the chord is 5N

In first four seconds the angular displacement of the disc is 40 rad

The work done by the torque on the disc in first four seconds is 200J

The increase in the kinetic energy of the disc in the first four seconds in 200J

Text Solution

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The correct answer is:

CHECK THE SOLUTION.

(a, b, c, d)

By FBD of particle

mg – T = ma

10–T = a ... (i)

By FBD of disc

TR = I ∝ = L ⇒ T=

T = Ma/2 = a …. (ii)

By eq. (i) and (ii)

a = 5 m/s 2 and T = 5N and ∝ = a/R = 5 rad/s 2 For angular displacement of disc :

θ = ω t + 1/2 ∝ t

Work done by torque

Δ K.E. = Δ w = 200 J

K 2 – K 1 = 200 J

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