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 K.E.
`mg xx 80 = (1)/(2)mupsilon^(2)`
` implies upsilon^(2) = 2 xx 10 xx 80 = 1600`
`impliesu= 40 m//s`
Hence choice is (a).