Posted by **Cecille** on Saturday, February 12, 2011 at 4:03pm.

I fire a tennis ball from an air cannon, straight up from ground level, at initial speed v0. At

the instant it reaches the top of its trajectory, I fire a second tennis ball at the same initial

speed. Air resistance is negligible. At what fraction of the maximum height reached by the

first ball do the two collide?

- Physics -
**bobpursley**, Saturday, February 12, 2011 at 4:43pm
start ball one at max height:

hf=maxheight-1/2 g t^2

ball two:

hf=vo*t-4.9t^2

but t is the same, and hf is the same:

set the two equations equal, and solve for t.

then having t, find hf.

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