A man standing on a lift throws a ball upwards with the maximum initial velocity he can and is found to be equal to 55 m/s. After what time the ball returns to his hand if (a) the lift is stationary, (b) the lift is moving up with a uniform velocity of 7 m/s, (c)the lift is moving down with a velocity of 7 m/s. Also given g = 9.8 m/s2