A ball is thrown vertically upwards with an initial velocity of 5 m/sec from point P as shown. Q is a point 10 m vertically below the point P. Then the speed of the ball at point Q will be : (take g = 10 m/s2 and neglect air resistance)
(A) 7.5 m/sec
(B) 10 m/sec
(C) 15 m/sec
(D) 17.5 m/sec