Lecture_11 - 2 T = 2 v = r a = r Torque Rotational...

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Rotational Motion
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Rotational Motion We've treated objects as point particles. Not always an accurate approximation. Newton's Laws work for other objects Need to learn how to analyze rotation
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Describing Rotational Motion s r Angular Position (measured in radians (rad))
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Describing Rotational Motion ω avg = Δθ Δ t ω = lim Δt 0 Δθ Δt α avg = Δω Δt α = lim Δt 0 Δω Δt
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Example Consider a compact disk spinning at a constant rate. How does the speed of the red ball compare to the speed of the green ball? How does the angular velocity of the red ball compare to the green ball Is the translational acceleration of the balls 0? Is the rotational acceleration of the balls 0?
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Period Recall that the time to complete one revolution, the period, is related to the circumference of the circle Also, in the time that it takes to complete one revolution So Similarly Circumference = 2 π r T = 2 π r v Δθ=
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Unformatted text preview: 2 T = 2 v = r a = r Torque Rotational equivalent of force torque. Related to force applied, distance from the pivot, and the angle between the radial direction and the force Variable Torques Rotational Inertia F = ma = I A constant for each object. Can be calculated Complete Analogy We can make substitutions into all of the equations we have seen so far to get the rotational equivalent (Newton's Second Law, constant acceleration equations, Equilibrium condition, etc.) Rotational Equilibrium Has condition that Tips: If a torque tends to make an object move counterclockwise, the torque is considered positive. Clockwise negative If the object is in rotational equilibrium, any point can be taken as a pivot point = Bridge Balance Example Walk the Plank...
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This note was uploaded on 12/07/2011 for the course PHYS 220 taught by Professor Chang during the Fall '09 term at Purdue University-West Lafayette.

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Lecture_11 - 2 T = 2 v = r a = r Torque Rotational...

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