sharon serves the volleyball to barbara with an upward veloc

sharon serves the volleyball to barbara with an upward velocity of 23 ft/s. the ball is 3.5 feet above the ground when she strikes it. how long does barbara have to react, before the volleyball hits the ground?

Solution

first ball will reach max.height with funal velocity =0

v= u -gt

u-gt=0

g = 32.15 ft/sec^2

t = u/g =23/32 = 0.715 sec

Now height reached by ball during this time h= 23^2/2*32.15 = 8.227 ft

Time taken by ball to reach ground from thi height: h = 1/gt^2

t = (2h/g)^1/2 =0.715 sec

So, total time she has to react before ball hits ground =   0.715 sec + 0.715 sec = 1.43 sec