Object is dropped from a cliff of unknown height. I'm on another planet without the knowledge of the planet's gravitational acceleration. The object takes 4.15s to reach the bottom. Again, from the top of the cliff I toss the object upwards to a height of 2m then it falls back to the cliff bottom. This takes 6.3s. I solved for the height of the cliff using the standard x=x+vt+1/2at^2 and yeilded -8.6115s^2(a). How can I move on with upward then downward equation with only knowing a=cliff height/8.6115s^2 and not knowing the initial velocity of the object being thrown upward. Any suggestions on what to start solving for first?