1.

A sphere of mass m moving with a constant velocity u hits another stationary sphere of the same mass and of coefficient of restitution (e). The ratio of velocities of the two spheres, after collision, will be

Answer»

`e/((e + 1))`
`((1 - e)/(1 + e))`
`1/e`
`((e + 1)/(e ))`

Solution :Here, `m_1 = m_ = m, u_1 = u , u_2 = 0`
LET `v_1, v_2` be their velocities after collision.
According to PRINCIPLE of conservation of linear momentum
`m u + 0 = m (v_1 + v_2) " or " v_1 + v_2 = u ""….(i)`
by defination , `e = (v_2 - v_1)/(u - 0) " or " v_2 - v_1 = EU "".....(ii)`
Adding (i) and (ii) , we get, `v_2 = (u(1 + e))/(2)`
SUBTRACTING (ii) from (i), we get, `v_1 = ((1 - e)u)/(2) :. (v_1)/(v_2) = (1 - e)/(1 + e)`.


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