A hammer and a feather are dropped at the same time from 4 feet, in a under a vacuum by an astronaut under the moons gravity.....
d2s/dt2=-5.2ft/sec^2
initial conditions: ds/dt=0 and s=4 when t=0.
So, I find ds/dt, is -5.2T+c, and v(0)=4.
So v(t)=-5.2t+c=0
now s(t)=(-5.2/2)*t^2+cx+x
I want to find t when S(t)=0
4=(-5.2/2)0^2+kt+c
c=4
I want t when s(t)=0.
0=(-5.2/2)t^2+kt+4
what now?