1. The problem statement, all variables and given/known data: A body is projected with 50m/sec at an angle of 53 degree with the horizontal. After what time velocity makes an angle 33.7 degree with horizontal. (tan 33.7 = 2/3) 2. Relevant equations: Mostly from 2-Dimension and maybe calculus. 3. The attempt at a solution: I've first picked up the second part of the question and tried to find out the height at 33.7 degree angle by using h = uSinθt - 1/2gt but in this, I can't decide that what u should I put because 50m/sec is at the ground level. Moreover, I also don't know the time, t. And thus this method can not be used. What could be the other way? Please guide me in layman's term.