physics
posted by Fabian .
An object is thrown downward with an initial speed of 5 m/s from a height of 78 m above the ground. At the same instant, a second object is propelled vertically from ground level with a speed of 50 m/s.
The acceleration of gravity is 9.8 m/s2. At what height above the ground will the two objects pass each other?
Answer in units of m.

The height of each is
h1=78+(5)t4.9t^2
h2=0+50t4.9t^2
set them equal, solve for t.
Then put time t into either, to solve for final height. 
The acceleration due to gravity on planet X is
one fifth that on the surface of the earth.
If it takes 3.9 s for an object to fall a certain
distance from rest on earth, how long would
it take to fall the same distance on planet X?