A block is released from rest from a height `h = 5m`. After travelling through the smooth curved surface it moves on the rough horizontal surface through a length `l = 8 m` and climbs on to the other smooth curve surface through a height `h'`. If `mu = 0.5` find `h'`.

Options

A. `2 m`
B. `3 m`
C. `1 m`
D. zero

Answer

C

Explanation

The force acting on the block and `N` , gravity and friction

`W_(f) + W_(f) + W_(gr) = D K`
Where `W_(N) = 0, W_(f) = - mu mgl`
and `W_(gr) = mg (h - h') and Delta K = 0`
Thus `- mu mgl + mg (h - h') = 0`
`h' = h - mu l = 5 - (1)/(2) xx 8 = 1 m`