In the arrangement shown in figure, 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) `2U cos theta` (b) `(U)/(cos theta)` (c) `(2U)/(cos theta)` (d) `U cos theta`

Answer

False

Explanation

For mass `m`
`T - mg = ma`….(i)
For mass `2m`
`2 mg - T - 2ma`….(ii)
From(i) and (ii) `a = g//3`
In second case` T- mg = ma'`
`2mg - mg = ma'`
`a' = g`