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Learn about kinetic energy, work-kinetic energy theorem, potential energy, and elastic potential energy in physics with explanations, formulas, and examples. Enhance your knowledge of energy concepts for a better understanding of physics principles.
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Work and Energy Energy
Kinetic Energy • Kinetic energy – energy of an object due to its motion • Kinetic energy depends on speed and mass • Kinetic energy = ½ * mass * (speed)2 • KE= ½mv2 • Energy is measured in Joules (J)
Work-Kinetic Energy Theorem • The net work done on an object is equal to the change in the kinetic energy of that object • Net work = change in kinetic energy • Wnet=ΔKE
Work-Kinetic Energy Theorem • Speed of the object and kinetic energy increase if work is positive • Speed of the object and kinetic energy decrease if work is negative • Kinetic energy is the work an object can do as it comes to rest • Kinetic energy is the amount of energy stored in an object
Potential Energy • Potential energy – energy associated with an object due to the position of the object • Relative and is based on a frame of reference • Abbreviated PE or U • Measured in Joules (J) • Two main kinds of potential energy • Gravitational and elastic potential energies
Gravitational Potential Energy • Gravitational potential energy (PEg) – potential energy associated with an object due to the position of the object relative to the Earth or some other gravitational source • Based on height from a zero level • Gravitational potential energy = mass * free-fall acceleration * height • PEg=mgh • As objects fall gravitational potential energy is converted to kinetic energy • At the zero level, the object no longer has any gravitational potential energy
Elastic Potential Energy • Elastic potential energy – the potential energy in a stretched or compressed elastic object • Energy of springs and rubber bands • Relaxed length – the length of a spring when no external forces are acting upon it • As the spring is compressed, elastic potential energy is stored in the spring
Elastic Potential Energy • Spring constant – a parameter that expresses how resistant a spring is to being compressed or stretched • Has units of Newtons / meters (N/m) • Elastic potential energy = ½ * spring constant * (distance compressed or stretched)2 • PEelastic= ½kx2