Question

The angular momentum of a particle changes from 0 to 720JS in 4 sec; the magnitude of torque acting will be

*1440Nm
*360Nm
*180JS
*4.5JS
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Answer 1

Correct question:
The angular momentum of a particle changes from 0 to 720 Js in 4 sec; the magnitude of torque acting will be

(a) 1440 Nm (b) 360 Nm (c) 180 J or N-m (d) 4.5 J or N-m

​

The correct answer to the given question is option (c) 180 J or N-m

Given:

Initial angular momentum of a particle = 0 Js

Final angular momentum of a particle = 720 Js

Time taken = 4 sec

To Find:
The magnitude of torque acting =?

Solution:

The torque is the rate of change of the angular momentum.

It is given by

τ = $\frac{Final \ angular \ momentum \ - \ Initial \ angular \ momentum}{ time \ taken}$

τ = $\frac{720-0}{4}$

τ = 720/4

τ = 180

Hence, the magnitude of torque acting will be 180 N-m.

The correct answer to the given question is option (c) 180 J

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