A spherical ball of mass `20kg` is stationary at the top of a hill of height `100m` , it rolls down a smooth surface to the ground , then climbs up another bill of height of `30 m` and final rolls down to a horizontal base at a height of `20 m` about the ground . The velocity attained by the ball is

Options

A. `10(m)//(s)`
B. `10sqrt(30)(m)//(s)`
C. `40(m)//(s)`
D. `20(m)//(s)`

Answer

C

Explanation

`mg(100)=mg(20)+(1)/(2)mv^2`
`v=40(m)//(s)`