Posted by **Sarah** on Thursday, August 31, 2006 at 11:15am.

A mass is dropped from a height of 30m, and at the same time from ground level (and directly beneath the dropped mass), and another mass is thrown straight up with a speed of 15 m/s.

a) How far apart are the two masses after 0.5 s?

b) Will the massses ever meet or pass each other? And if so will the meeting place take place while both masses are falling or when one is falling and the other is rising?

a) I got 30 - 15t

30-15(.5 seconds)=22.5 meters

b) I need help on this part of the queston.

Did I do part a correctly?

distance apart= 30- 1/2 g (t)^2 - 15t + 1/2 g t^2

distance apart= 30 -15t

t= .5 second

If they meet, distance apart is zero

solve for t.

See what the velocity of the ball thrown upwards is at that time. Is it positive (upward) or not.