posted by Anonymous .
A ball is thrown vertically upwards From the top of a building of height 29.4 m and with an initial velocity 24.5 m/sec. If the height H of the ball from the ground level is given by H = 29.4 + 24.5t - 4.9t², then find the time taken by the ball to reach the ground
4.9 t^2 -24.5 t -29.4 = 0
t^2 - 5 t - 6 = 0
(t-6)(t+1) = 0
t = 6 seconds (the -1 second is before release :)