Lecture13_Pushkar

# Lecture13_Pushkar - If you have issues with the exam you...

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Lecture 13 Purdue University, Physics 220 1 If you have issues with the exam you can check your exam papers in Rm 144 We will keep them there only until March 12.

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Lecture 13 Purdue University, Physics 220 2 Lecture 13 Rotational Kinetic Energy and Inertia PHYSICS 220
Lecture 13 Purdue University, Physics 220 3 Rotations: Axes and Sign When we talk about rotation, it is implied that there is a rotation “axis”. This is usually called the “z” axis (we usually omit the z subscript for simplicity). Use the right-hand rule to determine the direction of rotation. Counter-clockwise (increasing θ ) is usually called positive. Clockwise (decreasing θ ) is usually called negative . z + ϖ

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Lecture 13 Purdue University, Physics 220 4 Rotational Kinetic Energy Consider a mass M on the end of a string being spun around in a circle with radius r and angular velocity ϖ Mass has speed v = ϖ r Mass has kinetic energy KE = ½ M v 2 = ½ (M r 2 ) ϖ 2 Rotational Kinetic Energy is energy due to circular motion of object. M
Lecture 13 Purdue University, Physics 220 5 You and a friend are playing on the merry-go-round at Happy Hollow Park. You stand at the outer edge of the merry-go-round and your friend stands halfway between the outer edge and the center. Assume the rotation rate of the merry-go-round is constant. Who has greater angular velocity? A) You do B) Your friend does C) Same Because within the same amount of time you and  your friend both travel 2 π .   An Old Example

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Lecture 13 Purdue University, Physics 220 6 Who has greater tangential velocity?
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