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

A boy reaches out of a window and tosses a ball straight up with a speed of 10 m/s. The ball is 20 m above the ground as he releases it. Use energy to find:

1)The ball's maximum height above the ground.

2)The ball's speed as it passes the window on its way down.

3)The speed of impact on the ground.

2. Relevant equations

E_{total}= PE_{i}+KE_{i}=PE_{f}+KE_{f}

Vf^{2}-Vi^{2}=2AD

KE=mv^{2}

PE=mgy

h_{max}= v^{2}/ 2g

3. The attempt at a solution

I solved for the first part and got it right by using the formula for hmax and got 5.1 ,and then added 20 m and got 25.1 meters which is correct.

For the second part I used vf^{2}-vi^{2}=2ad

and I got 10 m which is also correct.

I am having trouble finding the third one; I tried applying vf^{2}-vi^{2}=2ad using 20 m and 25.1 m and both of them didn't work.

any suggestions.

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# Homework Help: Find the Speed at Impact

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