SOLUTION: A ball is thrown vertically upward with an initial velocity of 48 feet per second. The distance s (in feet) of the ball from the ground after t seconds is s=48t−16t2 .

Question 1206150: A ball is thrown vertically upward with an initial velocity of 48 feet per second. The distance s (in feet) of the ball from the ground after t seconds is s=48t−16t2
.
(a) At what time t will the ball strike the ground?
(b) For what time t is the ball more than 20 feet above the ground?
Found 2 solutions by mananth, greenestamps:
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
A ball is thrown vertically upward with an initial velocity of 48 feet per second. The distance s (in feet) of the ball from the ground after t seconds is s=48t−16t2
.
(a) At what time t will the ball strike the ground?
at t=0 the ball is on ground
S(t)=0 = 48t-16t^2
Solve for t
16t^2=48t
t=3s
(b) For what time t is the ball more than 20 feet above the ground?
Between two times it is above 20 ft
48t-16t^2 >20
Solve the inequality to get the time (s)
.

Answer by greenestamps(13198) (Show Source): You can put this solution on YOUR website!

(a) The ball hits the ground when s, the height of the ball above the ground, is zero:

and

ANSWER: at 3 seconds

(b) We want the height of the ball to be greater than 20 feet:

It's awkward to solve the quadratic inequality. Instead, solve an equation to find the times when the height of the ball is exactly 20 feet. Then use common sense to get the answer.

and

The ball is 20 feet off the ground at t=0.5 seconds and t=2.5 seconds, so it is more than 20 feet above the ground between those two times.

ANSWER: between t=0.5 second and t=2.5 seconds

RELATED QUESTIONS
A ball is thrown vertically upward with an initial velocity of 80 feet per second. The... (answered by Alan3354,ikleyn)
A ball is thrown vertically upward from the ground with an initial velocity of 103 feet... (answered by ikleyn)
A ball is thrown vertically upward with an initial velocity of 4848 feet per second. The... (answered by KMST)
a ball is thrown vertically upward with an initial velocity of 128 feet per second. The... (answered by josmiceli)
A ball is thrown vertically upward from the top of a building 144 feet tall with an... (answered by KnightOwlTutor)
A ball is thrown vertically upward from the ground with an initial velocity of 103 feet... (answered by ikleyn)
A ball is thrown vertically upward from the top of a building 64 feet tall with an... (answered by ikleyn,Boreal)
Please help me solve this: A ball is thrown vertically upward from the top of a... (answered by nerdybill)
A ball is thrown vertically upward from the top of a building 128 feet tall with an... (answered by stanbon,solver91311)

SOLUTION: A ball is thrown vertically upward with an initial velocity of 48 feet per second. The distance s​ (in feet) of the ball from the ground after t seconds is s=48t−16t2 .

SOLUTION: A ball is thrown vertically upward with an initial velocity of 48 feet per second. The distance s (in feet) of the ball from the ground after t seconds is s=48t−16t2 .