Feedback on the concepts surrounding pulley, ropes, friction

In summary, the conversation discusses revisiting the angles for two cases where the first angle is less than 90 degrees and the second angle is greater than 90 degrees. It is mentioned that friction can be used to reduce the pulling resisting force in relation to the greater load. The conversation also references the capstan equation and mentions that friction will aid the weaker force in this arrangement. It is noted that in the usual linear arrangement, the difference between the two forces must be less than a certain value for static friction, while in capstan arrangements, the difference between the natural logarithms of the two forces must be less than a certain value multiplied by the angle of contact. The conversation ends with a question about how friction would change if the second force
  • #1
goodOrBad
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Homework Statement
Having been working on problems that included weight, ropes, pulley and friction I wanted to make a sort of reminder. But I need to know if and what changes if F2 > F1
Relevant Equations
Fx=0
Fy=0
WhatsApp Image 2020-09-24 at 13.02.20.jpeg
 
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  • #2
Revisit the angles for the two first cases.
From first diagram, β<90°.
From second diagram, β>90°.
 
  • #3
really? Because I thought it goes like this
tri.png
 
  • #4
  • #5
goodOrBad said:
if and what changes if F2 > F1
Friction acts to oppose relative motion of the surfaces in contact. It will aid whichever of the two forces is weaker.
In the usual linear arrangement, ##|F_1-F_2|<\mu_sN## for static friction; in these capstan arrangements, ##|\ln(F_1)-\ln(F_2)|<\mu_s\theta##.
(I'm assuming each force is measured with pulling away from the frictional contact as positive.)
 
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1. What is a pulley and how does it work?

A pulley is a simple machine that consists of a wheel with a grooved rim and a rope or cable that runs along the groove. It works by changing the direction of the force applied to the rope, allowing a person to lift or move heavy objects with less effort.

2. How does friction affect the movement of a pulley?

Friction is the force that resists the motion of two objects in contact. In the case of a pulley, friction between the rope and the grooved wheel can reduce its efficiency and make it harder to lift heavy objects. Lubricating the pulley or using a smoother rope can help reduce friction and make the pulley more efficient.

3. Can a single pulley system lift an object by itself?

No, a single pulley system can only change the direction of the force applied to the rope. In order to lift an object, a person must use a combination of pulleys, such as a fixed pulley and a movable pulley, to create a mechanical advantage and reduce the amount of force needed to lift the object.

4. How does the number of ropes and pulleys affect the mechanical advantage?

The more ropes and pulleys used in a system, the greater the mechanical advantage. This means that a person can lift heavier objects with less force. However, using more ropes and pulleys also means that the distance the rope must be pulled is longer, so the work done remains the same.

5. How does the weight of the object being lifted affect the pulley system?

The weight of the object being lifted affects the mechanical advantage of the pulley system. The heavier the object, the greater the force needed to lift it. This means that a person may need to use more ropes and pulleys to create a larger mechanical advantage and make it easier to lift the object.

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