1. The problem statement, all variables and given/known data Two rocks are thrown off the edge of a cliff that is 15m above the ground. The first rock is thrown upward, at a velocity of +12m/s. The second is thrown downward, at a velocity of -12.0m/s. Ignore air resistance. Determine how long it takes the first rock to hit the ground and at what velocity it hits. Determine how long it takes the second rock to hit the ground and at what velocity it hits. 2. Relevant equations 3. The attempt at a solution 15=12t+.5(9.8)t^2 To figure out time I tried v/g=t (12/9.8) but it was coming out saying the answer was wrong.