A block of mass `M = 5 kg` is moving on a horizontal table and the coefficient of friction is `mu = 0.4`. A clay ball of mass `m = 1 kg` is dropped on the block, hitting it with a vertical velocity of `u = 10` m/s. At the instant of hit, the block was having a horizontal velocity of `v = 2` m/s. After an interval of t, another similar clay ball hits the block and the system comes to rest immediately after the hit. Assume that the clay balls stick to the block and collision is momentary. Find t. Take `g = 10 m//s^(2)`.