1. The problem statement, all variables and given/known data Whenever I solve a free-fall problem and it asks for the time, I never am sure what the time represents once I solve for it. I understand when you throw a ball in the air and it comes back down, the time it takes to ascend up, is the same time it takes to descend down. Therefore, whenever I'm attempting a free-fall problem, and it asks for the time the ball was in the air, whatever I get for time, using a kinematics equation, I always multiply by 2 because as I stated before, you have to consider the same amount of time it ascends up + the same amount of time it descends down. However, I will get problems wrong on my exam by multiplying by 2, and sometimes I won't multiply by 2 and I will get problems wrong because I didn't. Therefore, I just don't understand what time refers to in a free-fall problem. Sorry for the long explanation but I had to include my confusion. Here is an example of a problem where I multiplied by 2 and got it wrong: "A ball is shot straight up from the surface of the earth with an initial speed of 19.6 m/s. Neglect any effects due to air resistance, how much time elapses between the throwing of the ball and its return to the original launch point? 2. Relevant equations 3. The attempt at a solution V0 = 19.6 m/s a = -9.80 m/s2 y = 0 m t = ? I used equation y = (v0)(t) + 1/2(a)(t^2) solving for t I rearranged the equation to be t = 2(y-v0)/a t = 2[(0 m) - (19.6 m/2)] / (-9.8 m/s^2) t = 4 s Now what does this 4 seconds represent? Is it the total time the ball is in the air, or is it when the ball is ascending up and you have to remember that it descends the same amount of time as well, so multiply by 2? Because I assumed you had to multiply by 2 and left an answer of 8 seconds and got the problem wrong, it was 4 seconds. However, another student used a difference equation (v = v0 + at) and got 2 seconds as his answer, and left it as 2, and got it wrong because he did not consider the ascending and descending time. While typing this I think I just solved my own question...in order to realize what the time represents do I solve t for various other kinematic equations and see what other answers I get? The smaller time I get, then it's an indication that it's half the time it went up (or down) and therefore multiply by 2?