1. The problem statement, all variables and given/known data A projectile returns to its original height after 4.08 seconds, during which time it travels 76.2 meters horizontally. If air resistance can be neglected, what was the projectile's initial speed? (Use g = 9.80 .) 2. Relevant equations 3. The attempt at a solution Hey guys I already solved the problem I just want to get some feedback on whether my breakdown of what I did was correct. So what I did first was split the problem into its X and Y ( horizontal and vertical components). 76.2m=v0 (4.08s) vx=18.67m/s Then since the projectile returned to its original height this means that its displacement or change in position will be zero. So I can solve for its initial velocity , by doing the following 0=-.5(9.8)(4.08)^2+v0(4.08) v0=20m/s Here is where I get confused I know I have to do the magnitude formula to get the intial speed of 27.4. squaroot ((18.67)^2+(20)^2)) My question is why do I have to do that?