1. The problem statement, all variables and given/known data An astronaut on a distant planet wants to determine it's acceleration due to gravity. The Astronaut throws a rock straight up with a velocity of +15 m/s and measures a time of 20.0 s before the rock returns to his hand. What is the acceleration due to gravity on this planet. Velocity=15 m/s Time= 20.0s 2. Relevant equations v=Vo + at x=Vot + 1/2 a t^2 v^2= Vo^2 + 2ax 3. The attempt at a solution I have no clue where to start. Give me a hint please.