Energy the ability capacity to do work Energy
Energy the ability (capacity) to do work Energy comes in many forms: mechanical, electrical , magnetic, solar, thermal, chemical, etc. . . The SI unit of energy is the Joule. Energy, like work, is a scalar.
Kinetic Energy energy of motion All moving objects that have mass have kinetic energy. KE = 1/2 2 mv m - mass of the object in kg v - speed of the object in m/s KE - the kinetic energy in J
Work-Energy Theorem the net work done on an object is equal to its change in kinetic energy
A net force causes an object to change its KE because a net force causes an object to accelerate, and acceleration means a change in velocity, and if velocity changes, KE changes.
Potential Energy energy of position or condition gravitational potential energy PEg = mgh m - mass of object in kg g - acceleration of gravity in m/s 2 h - height of object, in m, from some arbitrary reference point PE – gravitational potential energy in J
Law of Conservation of Energy “Energy can neither be created nor destroyed. It may only change forms. ” S all types of energy before the event = S all types of energy after the event Examples: • A dropped object loses gravitational PE as it gains KE. • A block slides across the floor and comes to a stop. • A compressed spring shoots a ball into the air.
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