Question

i need help with a 1D physics problem.

A ball is thrown straight up from the ground with speed v0. At the same instant, a second ball is dropped from rest from a height H, directly above the point where the first ball was thrown upward. There is no air resistance.

Find the time at which the two balls collide.
Express your answer in terms of the variables H, v0, and appropriate constants..

Find the value of H in terms of v0 and g so that at the instant when the balls collide, the first ball is at the highest point of its motion.
Express your answer in terms of the variables v0 and g.

Answer 1

seems like this is two problems. the upball and then the downball

for the upball at some point we need to find the V(t) velocity at some time
we don't know the starting velocity V0 so V(t) = V0 - g*t g*t because the ball will slow at the speed of gravity 9.8 meters/second^2

If you threw the ball up at 9.8 it would reach 0 at t=1...so that seems to work

Answer 2

the position of the upball would be 1/2gt^2 since position is the integral of the velocity

the position of the upball when V(t) = 0 is the final position of the downball and the position of the downball will be 1/2a*t with an a of g....maybe