A steel ball of radius `2 cm` is initially at rest. It is struck head on by another steel ball of radius `4 cm` travelling with a velocity of `81 cm//s`. If the collision is elastic their respective final velocities are

Options

A. `63 cm/s, 144 cm/s`
B. `144 cm/s, 63 cm/s`
C. `19 cm/s, 100 cm/s`
D. `100 cm/s, 19 cm/s`

Answer

`(2)`

Explanation

As mass, `m = rho(volume) rho 4/3 pi r^(3)`
`m, alpha r^(3) so, v_(1) = ((r_(1)^(3) - r_(2)^(3))/(r_(1)^(3) + r_(2)^(3)))u_(1) and v_(2) = (2r_(1)^(3)u_(1))/(r_(1)^(3) + r_(2)^(3)`