The velocity of the block B is:

Options

A. `2ms^(-1)`
B. `3 ms^(-1)`
C. `1 ms^(-1)`
D. `6ms^(-1)`

Answer

C

Explanation

x + 2y = L (length of string)
`(dx)/(dt) + (2dy)/(dt) = 0 implies - (dy)/(dt) = (1)/(2) ((dx)/(dt)) v_(B) = (1)/(2) (2) = 1 ms^(-1)`
Applying tension trick,
`2T (V_(B)) - T (2) = 0 implies 2 T (V_(B)) = 2T :. V_(B) = 1ms^(-1)`