Torque on Pulley sitting on moving belt

In summary, the free body diagram for the pulley and the belt includes friction to the left, the applied force to the right, and the weight of the belt down and the normal force up. The force on the pulley is equal to the friction on the belt, as it is the friction that provides the torque and causes the pulley to rotate.
  • #1
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Homework Statement


There is a Pulley (or just a wheel) sitting on a moving belt being pulled with force Fa with some unknown friction between the pulley and the belt. The pulley rotates without slipping on the belt. Draw a freebody diagram of the pulley and the belt.


Homework Equations





The Attempt at a Solution



So I feel bad asking this question because it is so basic, but for some reason I am just stuck between two possibilities.

so for the belt my free body diagram looks like:
Friction to the left, the applied force to the right, and the weight of the belt down and normal force up.

Now for the Pulley:
Weight of the pulley down, normal force up.
Now, there is a Force to the right, which creates a torque on the pulley, due to the friction with the belt. My question is:

1) is the force to the right(on the pulley) = to the frictional force on the belt?

or

2) force to the right(on the pulley) = Force applied - Frictional force(both of the belt)

I believe the Torque on the pulley is only due to friction, so I would assume 1 is correct, but I've heard arguments for 2, and since 2 is a force to the right, since Fapplied > Ffriction, its been bugging me which is correct.

Thanks
 
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  • #2
! The correct answer is option 1. The force on the pulley is equal to the frictional force on the belt. This is because the friction between the belt and the pulley is what provides the torque that causes the pulley to rotate. Therefore, the force on the pulley must be equal to the friction on the belt, since it is this friction that is causing the pulley to rotate.
 

FAQ: Torque on Pulley sitting on moving belt

What is torque?

Torque is a measure of the force that causes an object to rotate around an axis or pivot point. It is a vector quantity, meaning it has both magnitude and direction. In other words, torque is the rotational equivalent of force.

How is torque calculated?

Torque is calculated by multiplying the force applied to an object by the distance from the axis of rotation to the point of application of the force. This distance is often referred to as the lever arm or moment arm. The resulting unit for torque is Newton-meters (N*m) in the metric system and foot-pounds (ft-lb) in the imperial system.

What is a pulley?

A pulley is a simple machine consisting of a wheel with a grooved rim and a rope or cable that runs along the groove. Pulleys are used to change the direction of a force, transmit power, or provide mechanical advantage.

How does a pulley on a moving belt affect torque?

If a pulley is sitting on a moving belt, it will experience two types of forces: the weight of the pulley and the tension force from the belt pulling on the pulley. The torque on the pulley will depend on the direction and magnitude of these forces, as well as the distance from the axis of rotation to the point of application of the force.

What factors affect the torque on a pulley sitting on a moving belt?

The torque on a pulley sitting on a moving belt can be affected by various factors such as the weight of the pulley, the tension force from the belt, the speed of the belt, the direction of rotation, and the friction between the pulley and the belt. Additionally, the number and arrangement of pulleys in a system can also affect the overall torque on a pulley.

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