Question

A ball it hit straight up in the air with an initial velocity of 12.9 m/s. At what time does it cross the height of 5 m going up?

Answer 1

5 = 12.9 t - 4.9 t^2
4.9 t^2 - 12.9 t + 5 = 0
t = 0.472 going up and 2.16 coming down