- #1
kftheuidfnaks
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- Homework Statement
- Does the force of friction on an object depend on the number of surfaces in contact with the object?
- Relevant Equations
- I attached an image describing my question.
The safe way is to consider each surface separately, making sure to use only the normal force that applies on that surface in each case.kftheuidfnaks said:Homework Statement: Does the force of friction on an object depend on the number of surfaces in contact with the object?
Homework Equations: I attached an image describing my question.
View attachment 253025
If the surfaces are of equal material, you essentially end up with twice the frictional force?haruspex said:The safe way is to consider each surface separately, making sure to use only the normal force that applies on that surface in each case.
It gets awkward if the angle between the surfaces is less than 90 degrees, since the normal forces partly oppose each other, leading to indeterminate forces.
No, that's not what I wrote. Consider e.g. when the angle is opened to 180 degrees. It is now one surface, so not doubled.kftheuidfnaks said:If the surfaces are of equal material, you essentially end up with twice the frictional force?
Am I thinking of your proposal wrong if I split the block in two, one left and one right of the center when its opened to 180 degrees?haruspex said:No, that's not what I wrote. Consider e.g. when the angle is opened to 180 degrees. It is now one surface, so not doubled.
Do the algebra. What is the normal force on each?
Unfortunately it is more complicated than that. The normal forces, by definition, act at right angles to the surfaces. So to find the contribution of each to supporting the weight you need to find the angles the surfaces make to the horizontal . This is a tricky bit of 3D geometry.kftheuidfnaks said:Am I thinking of your proposal wrong if I split the block in two, one left and one right of the center when its opened to 180 degrees?
Normal Force = (m/2)g*cos(Theta) + (m/2)g*cos(Theta)
N = mg*cos(Theta)
I'm not sure what the set-up is in the above diagrams. None of them match the diagram in post #1. In particular, none seem to involve two surfaces. Is that intentional?kftheuidfnaks said:View attachment 253028
Well I'm probably over-complicating this but I am trying to visualize the problem so I drew this.
Since each dimension has a contribution to the total Normal force, their magnitudes and directions need to get combined, right?
Multi-surface frictional force is the resistance force that occurs between two or more surfaces in contact when one surface moves or tries to move against the other.
Multi-surface frictional force is measured in units of force, such as newtons or pounds, using a device called a dynamometer. The force required to overcome the friction between two surfaces is measured and used to calculate the frictional force.
The factors that affect multi-surface frictional force include the type of surfaces in contact, the roughness or smoothness of the surfaces, the force pressing the surfaces together, and the presence of any lubricants.
Multi-surface frictional force can either help or hinder motion. In some cases, friction can provide necessary traction to allow an object to move. However, in other cases, friction can create resistance and slow down or prevent motion.
Multi-surface frictional force cannot be completely eliminated, but it can be reduced by using lubricants, choosing smoother surfaces, or decreasing the force pressing the surfaces together. In some cases, friction can be beneficial and necessary for certain tasks, such as walking or driving.