1.

A small block of mass `M` moves on a frictionless surface of an inclined plane, as shown in the figure. The angle of the incline suddenly changes from `60^(@)` to `30^(@)` at point `B`. The block is many at rest at `A`. Assume that collisions between the block id the incline are totally inelastic. The speed of the block at point `C`, immediately before it leaves the second incline A. `sqrt(120) m//s`B. `sqrt(105) m//s`C. `sqrt(90)m//s`D. `sqrt(75) m//s`

Answer» Correct Answer - D
Height fallen by the block from `B` to `C`
`h_(2)=3sqrt(3) tan30^(@)=3m`
Let `v_(3)` be the speed of the block, at point `C` just before it leaves the second incline, then
`v_(3)=sqrt(v_(2)^(2)+2gh_(2))=sqrt(45+2xx10xx3)=sqrt(105) m//s`


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