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Published byShannon Lindsey Modified over 8 years ago
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Energy Ability to do work or the Ability to make something happen
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Kinetic energy Energy something has because it is moving at a certain speed Linear E k related to objects mass and linear speed E k = 1/2m v 2
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E k units m (mass) in kg V (velocity) in m/s ◦ Once it is squared, units become m 2 /s 2 Measured in Joules which = Nm which = kg m 2 /s 2 English units will be ft lb
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Rotating objects Energy related to inertia (I) and angular speed ( ) E k = ½ I (
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Moment of inertia Depends on ◦ Location of axis around which object rotates ◦ Mass of object ◦ Distribution of mass around axis If mass is unevenly distributed, doesn’t rotate smoothly (vibrates or wobbles) MOI varies with each shape
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Moment in inertia (cont.) Center of mass – location at which an object’s mass is assumed to be concentrated If mass is unevenly distributed, doesn’t rotate smoothly (vibrates or wobbles)
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Kinetic energy Since E k = 1/2m v 2, objects with more mass have more KE for the same speed Since E k = 1/2m v 2, increasing speed increases KE by a LOT (v is squared!)
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Work-energy theorem Work = KE – the work-energy theorem (proposed by James Prescott Joule). Work is measure of energy transmitted by any kind of force (push-pull, p, v or T) Object’s total kinetic energy changes by amount equal to work done.
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Work and kinetic energy Work is measure of energy transmitted by force Work measured by change in KE of moving object ◦ - work means force applied is opposite object’s motion ◦ + work is in same direction as object’s motion
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Energy conversions Energy done by machines is usually accomplished by converting energy from 1 form to another Energy can be used, but no work done, if no motion occurs (W = F*d) Examples: ◦ Food (chemical) mechanical and heat (you, or the engine in a car) ◦ Electric mechanical potential (pump) All energy conversions create wasted energy (heat)
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Law of Conservation of Energy Energy is neither created nor destroyed. It only changes from 1 form to another. In other words, (like momentum and mass) energy is always conserved. The total amount before change = total amount after change.
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References used en.wikipedia.org/wiki www.ftexploring.com/energy/energy.html tutor4physics.com/positivenegativework.htm www.bibliotecapleyades.net/huntley/esp_huntley _11.htm www.bibliotecapleyades.net/huntley/esp_huntley _11.htm www.plumbingsupply.com/handpump.html www.cartoonstock.com/directory/E/Energy_co nservation.asp www.cartoonstock.com/directory/E/Energy_co nservation.asp www.fotosearch.com/photos-images/tug- war.html www.fotosearch.com/photos-images/tug- war.html www.gettyimages.com/detail/82719459/lifesize
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