# Questions About Rope Tension & Friction

• ndogg
In summary: If an object sits at rest on a record player's record that is moving around, where is its frictional force?1) If the object is at rest on the record, then the frictional force is zero.2) If the object is not at rest on the record, then the frictional force is directed towards the center of the record, where the record is moving the fastest.In summary, the object's frictional force is directed towards the center of the record where the record is moving the fastest.
ndogg
I have a few questions:

1) Does the weight of the rope (if it is significant) affect its tension?

2) Look at this picture: http://i14.tinypic.com/3ynt3cg.jpg

3) If an object sits at rest on a record player's record that is moving around, where is its frictional force?

ndogg said:
I have a few questions:

1) Does the weight of the rope (if it is significant) affect its tension?

2) Look at this picture: http://i14.tinypic.com/3ynt3cg.jpg

3) If an object sits at rest on a record player's record that is moving around, where is its frictional force?

1) Yes, it does, but it is never significant in introductory physics problems.

2) What do the FBD-s look like? Well, the first question you need to answer is: what forces act on the box?

3) The frictional force always points in the opposite direction of the direction of motion. (Hint: which force acts on an object in circular motion?)

1) What if the rope weighed 10kg and the weight of the object was 15kg?

2) Tension and weight, but I'm not sure what the FBDs look like.

3) Centripetal force -- so wouldn't frictional force point opposite of the force going into the circle, meaning it points outward.

1) You should find the center of mass of the rope and add the vector of its weight placed at the center of mass.

2) In what directions do tension and weight point? Now you have all the data do draw FDB-s.

3) Correct.

1) Picture this: A rope is hanging from a hook on the ceiling. At the bottom of the rope is a mass of weight 15 kg. The rope itself weighs 10 kg. What is the tension in the rope?

2) I should have clarified my drawing in the first mass of 7 kg to be a person holding the string with his hand. I'm assuming the forces that act on the person are his weight (70 N), and the tension from the 6 kg mass on the other side of the pully (60 N). But I'm not sure what forces act on the 6 kg mass.

1) Again, draw a FBD with the weight of the rope acting in its center. Maybe this might help - what is the magnitude of the force which the hook exerts on the rope?

2) Hint: does the 6kg mass have a weight?

1) The hook exerts a force of 150 N on the rope. So would the tension in the rope just be 150 N? Or do you have to take into account the mass of the 10 kg rope, in which case the tension would be 250 N or 200 N?

2) The 6 kg mass does not have weight because it is suspended in the air, right?

ndogg said:
2) The 6 kg mass does not have weight because it is suspended in the air, right?

Hint: in introductory physics textbooks, "weight" is usually a synonym for "gravitational force".

Oh yeah, I don't know what I was thinking. There is still weight, so the force pushing down is 60 N.

I still would like to have someone clarify #3.

## 1. How does rope tension affect friction?

Rope tension plays a crucial role in determining the friction between two surfaces. When there is more tension on a rope, the force acting on the rope increases, leading to a higher frictional force between the rope and the surface it is in contact with.

## 2. What is the relationship between rope tension and the coefficient of friction?

The coefficient of friction is a measure of how much resistance there is between two surfaces in contact. It is affected by various factors, including rope tension. As rope tension increases, the coefficient of friction also increases, resulting in a stronger grip between the rope and the surface.

## 3. Can rope tension be used to reduce friction?

Yes, in some cases, increasing rope tension can actually reduce friction between two surfaces. This is because the tension can help to smooth out any irregularities in the surfaces, creating a more even and smoother contact area.

## 4. How does rope material affect friction?

The type of material used to make a rope can significantly impact its frictional properties. For example, a rougher and more textured rope will typically have a higher coefficient of friction compared to a smoother and more slippery rope made of a different material.

## 5. Is there a limit to how much tension can be applied to a rope before it breaks?

Yes, every rope has a maximum tension limit, also known as its breaking strength. Applying too much tension can cause the rope to stretch or even break, which can be dangerous. It is important to know the breaking strength of a rope before using it to avoid any accidents.

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