1. The problem statement, all variables and given/known data You throw a rock of weight 20.4 N vertically into the air from ground level. You observe that when it is a height 14.9 m above the ground, it is traveling at a speed of 26.0 m/s upward. Use the work-energy theorem to find its speed just as it left the ground; Use the work-energy theorem to find its maximum height. Take the free fall acceleration to be g = 9.80 m/s^2. 2. Relevant equations Wtotal = delta K K = mv^2 v^2 = vi^2 + 2a(x-xi) 3. The attempt at a solution I believe this can also be done using kinematic equation, since we are given vf,x,a, and we want vi. So if this is true, I will attempt both ways :D 26^2 = vi^2 + 2(-9.8)(14.9-0) vi = 31.11 <--------> which is right now, for using the work energy theorem. we first need the mass. using w=mg 20.4 = m ( 9.8) m = 2.08 K1 = 1.2(2.08)(v)^2 K2 = 1.2(2.08)(26)^2 K2 = 843.65 K1 = 0 ....how do I proceed?