You throw a 20-N rock vertically into the air from ground level. You observe that when it is 15.0 m above the ground, it is traveling at 25.0 m/s upward. Use the work-energy theorem to find (a) the rock’s speed just as it left the ground and (b) its maximum height.

Solution 20E Step 1 of 2: a) We know that,According to work energy theorem W = K.E K.E grav 2 1 1 2 1 2 mgh = mv2 m2 2 1 Dividing by m 2 v1= v2+ 2gh = (25 m /s) + 2 × 9.8 m/s × 15 m = 30.3 m/s