Question

A playground is surrounded by a fence 2.0 m high. A boy who plays in the
playground kicks a ball vertically upward from a height of 0.2 m with a speed of
10 m/s. How much time does the ball spend above the height of the fence?

Answer 1

\[-4.9t ^{2}+v _{0}t+s=h\]
\[-4.9t^2+10t+.2>2\]
\[-4.9t^2+10t-1.8>0\]

Answer 2

Set that equal to 0 and solve. The roots are .2 sec and 1.8 sec . When t is between those 2 values, the ball will be above the fence. 1.8-.2 = 1.6 sec the ball will be above the fence.