Answer:
rock's speed just as it left the ground = 30.2 m/s
Explanation:
The work energy theorem explains that the change in kinetic energy between two points = workdone between the two points.
Mass of the rock = 3/9.8 = 0.306 kg
Kinetic energy as it leaves the ground = mv₀²/2 = 0.153 v₀²
Kinetic energy at the height it reached = m(24.9²)/2 = 0.306 × 24.9²/2 = 94.862 J
Work done by the force of gravity in between those two points = (-mgh) = - 3 × 14.9 = - 44.7 J
94.862 - 0.153 v₀² = - 44.7
0.153 v₀² = 94.862 + 44.7 = 139.562
v₀ = 30.2 m/s
