Kinematics and free falling objects

[lemurs]

alright got a question for my homework and am stuck on it...

here it is. If a ball is dropped from hieght H above ground and at the same instance, a ball is released from ground vertically. Determine the speeed of the second ball if the two balls are to meet at hieght of H/2 above ground.

with that info i am stuck I know that Intial velocity of the ball dropped =0 and that to calculate it disatance h/2 will use .5at^2.

but how to equate that to the second ball I am stuck.

help would be apprieciated

 

[berkeman]

Write the equation of motion for the 1st ball, showing its position as a function of time -- its motion is set, with no unknown variables. Solve for the time when the falling ball is at H/2.

Then write the equation of motion of the 2nd ball, showing its position as a function of time, with the initial velocity as the unknown. Then solve for Vo, given that you know what time t is for it to make it to H/2.