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Lectures 17 &amp; 18 - Potential Energy

# Lectures 17 &amp; 18 - Potential Energy - EARTH C OMET...

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26 mi/s COMET 500,000,000,000 tons What is thekinetic energy of theasteroid? Mass = 5 x 10 14 Kg Speed = 26 x 1600 m/s = 4 x 10 4 m/s Kinetic energy = 1/2 x M x V 2 = 4 x 10 23 J EARTH Hiroshima bomb = 5 x 10 13 J Thekinetic energy of thecomet equals to 8,000,000,000 Hiroshima bombs.

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Potential Energy Chapter 8
Potential Energy Potential energy is the energy associated  with the configuration of a system of objects  that exert forces on each other This can be used only with  conservative  forces When conservative forces act within an isolated  system, the kinetic energy gained (or lost) by the  system as its members change their relative  positions is balanced by an equal loss (or gain) in  potential energy. This is  Conservation of Mechanical Energy

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Types of Potential Energy There are many forms of potential  energy, including: Gravitational Electromagnetic Chemical Nuclear One form of energy in a system can be  converted into another
Systems with Multiple  Particles 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

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System Example This system consists of  Earth and a book Do work on the system by  lifting the book through  y The work done is       mg(y b  -  y a )  =           mgy b  -  mgy a
Potential Energy The energy storage mechanism is  called  potential energy A potential energy can only be  associated with specific types of forces  (conservative forces) Potential energy is always associated  with a system of two or more interacting  objects

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Gravitational Potential Energy Gravitational Potential Energy is associated  with an object at a given distance above  Earth’s surface Assume the object is in equilibrium and  moving at constant velocity The work done on the object is done by  F app   and the upward displacement is  r = D y ö j
Gravitational Potential Energy,  cont   The quantity  mgy  is identified as the  gravitational potential energy,  U g U g  =  mgy   Units are joules (J) W = Φ αππ ( 29 γ∆ρ = μγ ϕ ( 29 γ ψ β - ψ α ( 29 ϕ = μγψ β - μγψ α

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CPS Question
Gravitational Potential Energy,  final The gravitational potential energy depends  only on the vertical height of the object above  Earth’s surface In solving problems, you must choose a  reference configuration for which the  gravitational potential energy is set equal to

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