Hula Hoop Rotational Motion Problem

In summary, when throwing a hulahoop with back spin, the hoop initially moves to the right with speed v0 and rotates counterclockwise with speed ω0. At some point, it will change direction and start moving to the left, still sliding due to its rotation. Eventually, it will overcome the rotation and continue to roll to the left without slipping. The direction of the friction force in each case will be opposite to the direction of motion if there were no friction, with the hoop moving to the right in (1) and to the left in (2) and (3). This can be determined by considering the directions of linear and angular acceleration.
  • #1
elemons
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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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  • #2
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.
 

Related to Hula Hoop Rotational Motion Problem

1. What is the Hula Hoop Rotational Motion Problem?

The Hula Hoop Rotational Motion Problem is a physics problem that involves analyzing the rotational motion of a hula hoop as it spins around a person's waist. It is commonly used as an example to explain concepts such as centripetal force, angular velocity, and rotational inertia.

2. What is the equation for calculating the rotational motion of a hula hoop?

The equation for calculating the rotational motion of a hula hoop is:

ω = v/r

Where ω is the angular velocity, v is the linear velocity, and r is the radius of the hula hoop.

3. How does the speed of the hula hoop affect its rotational motion?

The speed of the hula hoop directly affects its rotational motion. As the speed increases, the angular velocity also increases. This means that the hula hoop will rotate faster and require a greater centripetal force to keep it spinning in a circular path.

4. What is the role of centripetal force in the Hula Hoop Rotational Motion Problem?

Centripetal force is the force that keeps the hula hoop moving in a circular path. In the Hula Hoop Rotational Motion Problem, the force of gravity provides the centripetal force, pulling the hula hoop towards the center of rotation.

5. How does the size and weight of the hula hoop affect its rotational motion?

The size and weight of the hula hoop affect its rotational motion by changing its moment of inertia. A larger and heavier hula hoop will have a greater moment of inertia, making it more difficult to spin and requiring a greater centripetal force to keep it rotating.

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