Friction Misunderstanding?

• bkhan90
In summary, the author is seeking further validation of their claim that friction between the pad and rotor is independent of the contact area between the pad and rotor. They propose testing the hypothesis by comparing the critical angle and times for sliding down an inclined plane using different contact areas.

bkhan90

I saw this post on a forum and thought it wasn't right, it's about why the force of frction on rotors is independent of the surface area of the calipers in contact with the rotors. I thought this was wrong because friction is a non conservative force, but am seeking further validation

the post:
Not really. Friction between the pad and the rotor is what stops you. And friction force is only dependent on the normal force and the coefficient of friction. The normal force is the force that is perpendicular to the direction of travel, which, in this case, is the force the pads apply on the rotor. So, since friction only depends on that force and the coefficient of friction (which depends on the material of the pad and rotor), the surface area of the contact patch has no effect on the braking performance. So, you may ask, why don't we use the smallest pads possible? Well, the more force we try and apply to a small area, the more likely that small area has of failing under the stress. So if we get more of a contact patch, that force is distributed more throughout the pad and rotor. But, braking performance and contact patch has no relation.

Surface area is part of the coefficient of friction.

bkhan90 said:
So, you may ask, why don't we use the smallest pads possible? Well, the more force we try and apply to a small area, the more likely that small area has of failing under the stress. So if we get more of a contact patch, that force is distributed more throughout the pad and rotor. But, braking performance and contact patch has no relation.
Ok. Let's reduce the size of the pads by a factor of 10. They might be a little less expensive to replace. I would then have them replaced every time I have the oil changed, and maybe have the rotors turned also. No thank you.

This claim is simple enough to test.

Get two objects of different dimensions and the same weight... say, a box covered with sandpaper.

Let it slide down an inclined plane.

Measure the critical angle and the times required for various angles.

The hypothesis: more surface area means greater critical angle and longer times for sliding down.

The null hypothesis: there is no difference, or the inverse of the hypothesis.

Air resistance is going to be negligible if you use fairly rough surfaces.

1. What is friction misunderstanding?

Friction misunderstanding is a common misconception about the nature and effects of friction. It is the incorrect belief that friction always slows down or hinders motion, when in fact, friction can also be used to increase or control motion.

2. What causes friction?

Friction is caused by the microscopic roughness of surfaces in contact with each other. As these rough surfaces rub against each other, they create resistance and slow down motion.

3. How does friction affect motion?

Friction can either increase or decrease motion depending on the circumstances. For example, friction in car brakes helps to slow down and stop the car, while friction in bike tires helps to increase traction and maintain balance while riding.

4. Can friction be eliminated?

No, friction cannot be eliminated completely. Even when surfaces are smooth, there is still a small amount of friction present. However, friction can be reduced through the use of lubricants or by using materials with low coefficients of friction.

5. What are the practical applications of friction?

Friction has many practical applications in our daily lives. It helps us to walk, drive, and even hold objects. Friction is also used in machines and tools to increase or decrease motion, such as in pulleys, gears, and brakes.