1. The problem statement, all variables and given/known data A toy rocket engine is securely fastened to a large puck that can glide with negligible friction over a horizontal surface, taken as the xy plane. The 4.00-kg puck has a velocity of 3.00ˆi ms at one instant. Eight seconds later, its velocity is (8.00ˆi + 10.0ˆj) ms. Assuming the rocket engine exerts a constant horizontal force, find (a) the components of the force and (b) its magnitude. 2. Relevant equations ΣF = m*a a = ΔV/Δt 3. The attempt at a solution Well, I took the all the info and applied it on the various formulas I know, and found the correct results, according to the book. So my problem doesn't lie there, as it's a simple problem of putting the correct quantities in the correct "positions". My problem lies more with "conceptualizing" the problem. I also checked the manual, but I can't understand one thing: It says that the force that the engine exerts on the puck is horizontal, so I take it that means the X part of the XY axis', correct? So, if this force is horizontal, then how can he ask me about its component of the net force? Does the statement mean that it's not horizontal per se, just that it acts on the first quadrant? Apart from that, how does the puck develop a velocity at the Y/vertical plane? From what I understand from the statement, it's a standard round puck on top of a, say floor, and I've put an engine on the back, that exerts a horizontal F force on it, causing it to move horizontally, but it somehow develops a velocity at both planes. Could anyone explain to me what exactly I'm missing? Thanks!