Solve problem related to object falling from rest

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Object falling from rest

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.

Potential Energy = Mass x Gravity x Height
PE = mgh

Kinetic Energy = ½ mv2
KE = ½ mv2

By conservation of energy
Energy before = Energy after
Initial KE + Initial PE = Final KE + Final PE
conservation of energy - Initial KE + Initial PE = Final KE + Final PE

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.

We can rewrite above equation
Initial PE = Final KE
potential energy = kinetic energy

The mass m on both sides tells us that the final velocity doesn’t depend upon the mass.
Velocity just before the impact is final velocity


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