Question

A ball is thrown vertically upward with an initial velocity of 64 feet per second. The distance(in feet) of the ball from the ground after t seconds is s=64t-16t.

At what time will the ball strike the ground?

For what time t is the ball more than 28 feet above the ground.

The ball will strike the ground when t is _____ seconds.

The ball is more than 28 feet above the ground for the time t when ____<t<____.

Answer 1

you should proably first simplify 64t-16t = 48t. Then, 48t=s. Plug it in, see what you get.

Answer 2

s = 64t - 16t^2
s=0 at t= 0,2

ball is more than 28 ft high when

64t - 16t^2 > 28
-16t^2 + 64t - 28 > 0
-4(2t-1)(2t-7) > 0

1/2 < t < 7/2