The question was: A 4.5-kg mass is given an initial velocity of 14 m/s up an incline that makes an angle of 37o with the horizontal. When its displacement is 8.0 m, its upward velocity has diminished to 5.2 m/s. I'm confused with directions of the velocity. In the solution they used the equation vf2=vi2+2*a*d anyway to find 'a' they subtracted (142-5.22)/(2*8) So doesn't this mean initial velocity and the upward velocity are parallel since they are being subtracted. I assumed the initial velocity would be parallel to the incline and the upward velocity completely vertical and thus i would have to 5.2/sin37. When you read the question, what direction would you assume? Maybe it's right and i'm just mixing up the axis?