Mechanical Energy and Free Fall – Basic Principles
How it works
Mechanical energy includes the kinetic (motion) energy and the potential (position) energy of a body. In free fall from rest, potential energy is converted into kinetic energy. The sum of potential and kinetic energy remains constant if air resistance and friction are neglected. For a body that falls from rest, the fall speed then depends on the height of the fall and on gravitational acceleration. Mechanical work, with constant force in the direction of motion, is the product of force and distance.
The total mechanical energy remains conserved in a closed system without energy losses: E_mech = E_pot + E_kin. Potential energy is calculated as m·g·h, kinetic energy as 0.5·m·v². In free fall from rest without air resistance, potential energy is converted into kinetic energy; from this follows for the speed v = √(2·g·h).
An example
A ball (m = 0.2 kg) falls from a height of 5 m. What potential energy does it have before the fall? (g = 9.81 m/s²)
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50 Exercises
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