Problema Solution
Jennifer serves the volleyball to Laura with an upward velocity of
12.5ft/s. The ball is
4 feet above the ground when she strikes it. How long does Laura have to react, before the volleyball hits the ground?
Answer provided by our tutors
Teh equation that describes the height of the ball is:
H = -16t^2 + Vot + Ho, where Vo is the initial velocity and Ho the initial height.
In our problem it is given that:
Vo = 12.5 ft/s
Ho = 4 ft
We plug the values into the equation:
H = -16t^2 + 12.5t + 4
Laura needs to react before the ball hits the ground.
When the ball hits the ground H = 0 so we need to solve the quadratic equation:
-16t^2 + 12.5t + 4 = 0 and find the positive roots
........
click here to see the equation solved for t
........
t = 1.03 s approximately
Laura has to react in the next 1.03 seconds.