(adsbygoogle = window.adsbygoogle || []).push({}); Known: v, t, and a .... cannot find Δy

Long time lurker, first time poster. Thanks for all the help y'all provide.

Problem #1:

1. The problem statement, all variables and given/known data

Wrongly called for a foul, an angry basketball player throws the ball straight down into the floor. If the ball bounces straight up and returns to the floor 2.5s after first striking it, what was the ball's greatest height above the floor?

2. Relevant equations

Only know three so far:

Y=Y_0 + Y_0t + ½ at²

V=V_0 + at

V²=V_0² + 2aΔx

3. The attempt at a solution

Used the top equation, since I knowtand need to knowy. I'm under the impression that this is a freely-falling objects question, so:

y_0 = 0 (the floor)

initial velocity = 0, at the very point the ball reverses direction to start its ascent

t = 2.5 seconds (given)

a = -9.8 m/s² (gravity)

y = 0 + 0t + ½(-9.8)(2.5)² = 30.625m

This is an incorrect answer, of course. I keep thinking there needs to be an initial velocity, but it's not given, and the only other way I know to calculate velocity is Δx/Δt, and I'm obviously trying to find Δx (or rather, Δy in this case). Any pointers would be most appreciated. Thanks!

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# Homework Help: Known: v, t, and a cannot find Δy

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