Chapter 8 Notes

# Chapter 8 Notes - Chapter 8 Notes Potential Energy o In the...

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Chapter 8 Notes - Potential Energy o In the case in which work is done on a system and the only change in the system is in its speed, the work done by the net force equals the change in kinetic energy of the system Work-Kinetic Energy Theorem o Potential Energy It is another form of energy associated with the configuration of a system of objects that exerts forces on each other o Potential Energy II There are many forms of potential energy, including: Gravitational Electromagnetic Chemical Nuclear One form of energy in a system can be converted into another o Potential Energy III We can extend our definition of a system to include multiple objects The force can be internal to the system The kinetic energy of the system is the algebraic sum of the kinetic energies of the individual objects Sometimes, the kinetic energy of one of the objects may be negligible - Conservative Forces o The work done by a conservative force on a particle moving between any two points is independent of the path taken by the particle o The work done by a conservative force on a particle moving through a closed path is zero Closed path- beginning and ending points are the same o Some conservative forces: gravity, spring force o We can associate a potential energy for a system with any conservative force acting between members of the system This can be done only for conservative forces In general W C = - U - Gravitational Potential Energy o This system consists of Earth and a book o Do the work on the system by lifting the book through y

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The work done is mgy b mgy a o Gravitational Potential Energy II Where did the work go? Stored in the configuration of the system The energy storage mechanism is called potential energy A potential energy can only be associated with specific types of forces o Potential energy is always associated with a system of two or more interacting objects o Gravitational Potential Energy III Gravitational potential energy is associated with an object at a vertical height above Earth’s surface The quantity mgy is identified as the gravitational potential energy, U g U g = mgy Units are joules (J) Reference where U g = 0? (Earth’s surface) Arbitrary normally need the difference in potential energy independent of the choice of reference - Elastic Potential Energy o Elastic Potential Energy is associated with a spring o The force the spring exerts on a block F S = - kx o The work done by an external applied force on a spring-block system
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## This note was uploaded on 04/17/2008 for the course PHYS 31 taught by Professor Dishaw during the Winter '08 term at Santa Clara.

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Chapter 8 Notes - Chapter 8 Notes Potential Energy o In the...

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