A body of mass m is whirled in a vertical circle by the hel…

Physics Motion in a Plane Mix MCQ (Single Correct)

A body of mass m is whirled in a vertical circle by the help of a ideal string fixed at one end, then –

tension in string may be mg only once in one complete circular path

tension in string may be equal to mg twice in one complete circular path

speed of body may becomes equal at only two time instants in one complete circular path

speed of body may becomes equal at more than two time instants in one complete circular path

Text Solution

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The correct answer is:

CHECK THE SOLUTION.

(b, c):

As T = mg ⇒ mg – mg cos θ =

= gr (1 – cos θ ) ….(1)

Also v 2 = u 2 – 2gr (1 – cos θ ) ….(2)

∴ 3gr (1 – cos θ ) = u 2

or, cos θ = 1 –

∴ At A and B tension are same to mg and speed

are also equal.

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