(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

To find the height of an overhead power line, you throw a ball straight upward. The ball passes the line on the way up after 0.85 s, and passes it again on the way down 1.2 s after it was tossed.

(a) What is the height of the power line?

(b) What is the initial speed of the ball?

2. Relevant equations

v = v0 + at

x=x0+v0*t + 1/2*a*t^2

x = x0 +v*t - 1/2*a*t^2

v^2 = v0^2 +2*a*(x-x0)

3. The attempt at a solution

I drew a picture and decided to solve for intial speed first. I used the equation v = v0 + a* t . V=0, a = -9.8m/s^2 and i took time at v0 to be 1.25 + 0.85/2 = 1.05 s

V0 = 10.29m/s

I then solved part a by using V^2 = V0^2 + 2 *a*(x-x0)

0=(10.29)^2 +2(9.8)(x-0)

i solved this and ended up with 5.40m

I got both of these wrong on my practice test. I would greatly appreciate if someone could explain to me what i did wrong. Thanks so much!

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# Homework Help: Kinematics free fall problems part 3 help

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