A spherical shell of mass 20 kg is stationary at the top of a hill of height 100 m. It rolls down a smooth surface to the ground, then climbs up another hill of height 30 m and finally rolls down to a horizontal base at a height of 20 m above, the ground. The velocity attained by the ball is :

Options

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

Answer

a

Explanation

Loss in potential energy = Gain in KE
`mgxx80=1/2mv^2`
`implies v^2=2xx10xx80=1600`
`implies v=40 m//s`