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06-46 Adding Friction

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    Now I confess, I've been oversimplifying it because we haven't talked about friction.
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    Now even though energy can never ever be created or destroyed,
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    friction in a way removes energy from a system.
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    Now what do I mean by that. Well before we ??? let's say a ball dropping from some height.
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    Well, we can think of this as energy converting from gravitational potential
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    to a kinetic energy as it moved in.
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    All of the gravitational I want to connect, but in reality that's not what happens.
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    All of the gravitational potential energy does not get convert to kinetic energy.
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    How did friction do this? How does it remove energy if energy can't be created or destroyed?
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    Well before when we look at, let's say a block sliding down a plane.
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    We visualized this as gravitational potential energy
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    getting converted to kinetic energy as the block moved down, but let's think about that.
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    As this blocks slides down, it's rubbing against this plane.
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    Go ahead and rub your hands together for a second and do it really hard.
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    They get really hot. In fact, friction creates heat. This heat is another form of energy.
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    If we start with a certain amount of gravitational potential energy,
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    some of it gets converted to useful kinetic energy, but some gets lost as heat.
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    The energy is still there, it's just that we can't really use it anymore. It's lost as heat to the atmosphere.
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    Now depending on the material of this plane or other situational factors, the fraction of this energy
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    that gets converted to heat can change,
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    maybe a lot of this energy gets converted to heat maybe almost none of it.
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    So let's consider these three cases.
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    In the first case, we have an object falling and let's say it's falling to what's called vacuum
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    so there's no air, it's just falling through empty space
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    Another example of object sliding down this rough jagged surface.
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    Another we have an object sliding down a relatively smooth surface.
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    What I want to know is, which of this diagrams corresponds to which of this pictures.
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    So in this diagram all of the potential energy is getting converted to kinetic energy
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    and here most of it is getting converted to heat, but in here only a small portion gets converted to heat.
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    Enter the appropriate number into the appropriate box.
Title:
06-46 Adding Friction
Description:

All units in this course below:

Unit 1: http://www.youtube.com/playlist?list=PLF79FCD2E20F4F9FC
Unit 2: http://www.youtube.com/playlist?list=PL0E63503E8232BB23
Unit 3: http://www.youtube.com/playlist?list=PL9BF147060D26ADF6
Unit 4: http://www.youtube.com/playlist?list=PLDB3B73A8BCD831C3

Join the class at http://www.udacity.com to gain access to interactive quizzes, homework, programming assignments and a helpful community.

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Team:
Udacity
Project:
PH100 - Intro to Physics
Duration:
02:03
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