Hula Hoop Rotational Motion Problem

AI Thread Summary
The discussion focuses on the dynamics of a hula hoop thrown with backspin, detailing its motion and the role of friction. Initially, the hoop moves to the right while rotating counterclockwise, leading to a leftward friction force that slows it down. As the hoop changes direction and begins to slide left, the friction continues to act leftward due to the opposing motion of the surfaces. Eventually, when the hoop rolls without slipping, the friction force will adjust accordingly to maintain this condition. Understanding the relationship between linear and angular motion is crucial for determining the direction of friction throughout the hoop's trajectory.
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Homework Statement


In throwing a hulahoop with back spin, you toss the hoop to the right, and it (1) moves right with speed v0, but rotates ccw with speed ω0. At some point, O, (2) it will change direction, and at that point it will start moving to the, left, but still be sliding because it is rotating too quickly. Finally, (3) it will overcome the rotation and continue to roll to the left without slipping. What direction does the friction point in each of these cases? How do you know?


Homework Equations





The Attempt at a Solution



For (1):
Friction force is left because motion is to the right and the hoop is slowing down

I don't know how to approach 2 and 3. I tried drawing the free body diagrams, and my text suggests I consider directions of linear and angular acceleration, but I don't know how this will help me!
 
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To work out which way friction will act at a contact, think about which way the surfaces would move in relation to each other if there were no friction. Friction will always act to oppose that motion.
 
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