Work Power and Energy 4 Question 2

3. A bob of mass M is suspended by a massless string of length L. The horizontal velocity v at position A is just sufficient to make it reach the point B. The angle θ at which the speed of the bob is half of that at A, statisfies

(2008,3M)

(a) θ=π4

(b) π4<θ<π2

(c) π2<θ<3π4

(d) 3π4<θ<π

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Answer:

Correct Answer: 3. (d)

Solution:

  1. As,

v=5gLv22=v22ghh=L(1cosθ)

Solving Eqs. (i), (ii) and (iii), we get

cosθ=78 or θ=cos178=151



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