As an object falls from rest, its gravitational potential energy is converted to kinetic energy. Consider a mass m which is falling vertically under the influence of gravity.
Object is falling from rest, therefore initial kinetic energy is zero. Once the object hit on the ground, height is zero, therefore no potential energy at ground level.
Initial PE = Final KE
Impact velocity just before the impact is
From work-energy principle, change in the kinetic energy of an object is equal to the net work done on the object.
For a straight-line collision, the total work done is equal to the average force of impact times the distance traveled during the impact.
Average impact force x Distance traveled = Change in kinetic energy
Total work done = Kinetic energy just before object hit the ground
Use this simple tool to solve physics problem related to impact force from falling object.