1)A ball is thrown upward with an initial velocity of v = 20 m/s. How long is the ball in the air? What is the greatest height of the ball? When is the ball 15 m(adsbygoogle = window.adsbygoogle || []).push({});

above the ground?

1) I have figured out

t total = 4.08s

greatest height = 20.4m

For the last bit (Finding the time when x=15m), I am having trouble. I know the answer but cannot work it through.

Do I use s = ut+1/2at^2 for it?

If I do, it wont work out because the 20.4 m has to come into it, doesnt it?

Please help!

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# Homework Help: Ball projectile physics

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