A ball is thrown up from the top of a tower at 20 m/s velocity. It took the ball 6 sec to fall to the bottom. How high is the tower?
60
u = + 20 m/s ; a = - 10 m/s2 ; t = 6s
∴ s = ut + 1/2 at2
= 20(6) + 1/2 (- 10) 62 = 120 - 5 × 36
= 120 - 180 = - 60m