Question

You throw a ball straight up into the air as hard as you can. If it takes the ball 3 seconds to land back in your hand, how fast did you throw the ball?

Answer 1

Answer:

Step-by-step explanation:

I used the displacement equation from Physics to solve this cuz it was easiest to do it that way.  The displacement equation is

Δx = v₀t + .5at²

where Δx is the displacement of the ball in feet, v₀ is the initial upwards velocity in feet/sec, a is the acceleration due to gravity (which has a constant value of -32 ft/sec/sec), and t is time in seconds.

If the ball lands right back where it started, its displacement is 0.  We know the pull of gravity, and we are given the time as 3 seconds.  Filling in our equation and solving for the velocity:

$0=v(3)+.5(-32)(3)^2$ and

0 = 3v - 144 and

144 = 3v so

v = 48 ft/sec