Ball thrown striaght up part C

[Toranc3]

Homework Statement

A ball is thrown straight up from the edge of the roof of a building. A second ball is dropped from the roof 1 second later. You may ignore air resistance

If vo is greater than some value vmax, a value of h does not exist that allows both balls to hit the gorund at the same time. Solve for vmax.

Homework Equations

y=yo+vo*t+1/2*a*t^(2)

The Attempt at a Solution

I am not sure how to start it. Can somebody give me some hints?

 

[haruspex]

Presumably h is the height of the roof. Write down equations, one for each ball, for the height of the ball at time t. Make sure to use different variable names as appropriate (not making them both just 'y'). Using those equations, write the statement that each is on the ground at some time t_g.