Kinematics Help

[zhe0001]

da hello oh da hello

prease help with this question, can't get how to get the answer: h=50 above ground

A girl at the bottom of a 100 m high cliff throws a tennis ball vertically upwards. At the same instant, a boy at the very top of the cliff drops a golf ball so that it hits the tennis ball while both balls are still in the air. The acceleration of both balls can be taken as 10.0 m/s2 downwards.

If the balls collide when the tennis ball is at the top of its path, what is the position of the tennis ball when it strikes the golf ball?

Thanks!

[lzxnl]

da hello oh da hello

prease help with this question, can't get how to get the answer: h=50 above ground

A girl at the bottom of a 100 m high cliff throws a tennis ball vertically upwards. At the same instant, a boy at the very top of the cliff drops a golf ball so that it hits the tennis ball while both balls are still in the air. The acceleration of both balls can be taken as 10.0 m/s2 downwards.

If the balls collide when the tennis ball is at the top of its path, what is the position of the tennis ball when it strikes the golf ball?

Thanks!

For the boy, position = 100-5t^2 as the ball is dropped
For the girl, position = ut-5t^2, same t.
So we want the time of collision to coincide with 0=u-gt as for the ball to be at max height, v=0 (constant acceleration formulas everywhere here)
so u=10t
sub in second equation
10t^2-5t^2=position=5t^2=100-5t^2
5t^2*2=100
5t^2=50
So 100-5t^2=position of ball = 50