Question

A block of mass m is released from rest at point A. The compression in spring (force constant k) when the speed of block is maximum is found to be nmg cos $\theta$/4k. What should be the value of n?

• A. 5
• B. 4
• C. 6
• D. 7

Answer 1

The correct option is B 4

Sol.

The maximum compression in spring when the speed of the block is maximum and this happens only when the force of spring is equals to force exerted by block on the string.

$kx=\mathrm{mg}\cos \theta$

$x=\frac{\mathrm{mg}\cos \theta }{k}$

given,

$\frac{\mathrm{mg}\cos \theta }{k}=n\mathrm{mg}\frac{\cos \theta }{4k}$

$\therefore n=4\text{Ans}$