1. The problem statement, all variables and given/known data I saw this in a video about solving projectile motion problems and I was confused, I think I may have seen the same thing in my textbook: The question says: A soccer player on a level playing field kicks a soccer ball with a velocity of 9.4 m/s at an angle of 40 degrees above the horizontal. Determine the soccer ball's maximum height. vi=6.042m/s, a=-9.8m/s, vf=o m/s 2. Relevant equations vf^2=vi^2+2a(displacement) 3. The attempt at a solutIon I saw this in a video and I wasn't trying to solve it myself. But, I was confused because the initial velocity used was calculated previously as the initial velocity for the y component of the motion since this is projectile motion and it has 2 components. The final velocity is the velocity at the maximum height- om/s. But, the thing that confused me was that acceleration was stated to be -9.8m/s^2. If this question is taking the initial velocity from when the ball was thrown and the final velocity at the point at which the ball is at its maximum height, is it not then looking at the ball's motion from when it is thrown up until it reaches it's maximum height only- it's looking at the ball's motion as it is moving upwards. So, why is the acceleration given as if the ball were in free fall because that is the acceleration used in problems where an object is in free fall. Sorry this is so long, I just wanted to make sure that what I was saying made sense. Could someone please explain this to me, I'm really confused.