Question

The arrangement shown in Fig., the ends P and Q of an unstretchable string move downwards with uniform speed U. Pulleys A and B are fixed Mass M moves upwards with a speed

• A. $2Ucos\theta$
• B. $U/cos\theta$
• C. $2U/cos\theta$
• D. $Ucos\theta$

Answer 1

The correct option is B $U/cos\theta$

Here, Let the speed of the mass be $"V"$.

The point where mass is attached to the thread kill also have the same velocity.

Along the thread, the component would be $"V\cos \theta "$

Given, that threads more with velocity $=\mu$

$\therefore$ $V\cos \theta =\mu$

$\Rightarrow V=\frac{u}{\cos \theta }$