A small block of mass `M` move on a frictionless surface of an inclimed from as down is figure . The engle of the inclime suddenly change from `60^(@)` to `30^(@)` at point `B` . The block is initally at rest at `A` Assume the collsion between the block and the incline are totally inclassic `(g = 10m//s^(2)`)

The speed of the block at point `C` immediately before is leaves the second incline is

Options

A. `sqrt120 m//s`
B. `sqrt105 m//s`
C. `sqrt30 m//s`
D. `sqrt75 m//s`

Answer

B

Explanation

`v_(c )^(2) = v_(B)^(2) + 2g(h_(2) -h _(1)`
`rArr = v_(c ) = sqrt(45^(2) + 2 xx 10 xx 3) = sqrt(105) ms^(-1)`