Does increasing the load change the coefficient of static friction or kinetic friction?

Question

I need to know if the coefficient of friction will change if i change the load on a block. I believe that myu will not change unless you change the surface that the block slides on.

Do you believe that this is a valid answer?
Increasing the load will not change either coefficient of friction because the load doesn't effect the ratio of the force of friction to the normal force.

I also need to an explanation. Thank you.

Answer 1

No, it won't change. It's an inherent property that depends on the block and the ramp. Putting more load on it won't change this.

Answer 2

I disagree. A car wear it's front tyres quicker than the back tyres. This is because the front is were the motor sits putting more mass (Load) on the tyres. Hence both surfaces of both pairs of tyres being the same there is a difference in wear and tear due to a load difference. Now, the question you have asked is, Does increasing the load change the coefficient of static friction or kinetic friction? I am not sure if i'm missing something but it's implying that that increasing the load does change a coefficient, but which one. I believe the answer is kinetic friction.

Answer 3

In the usual idealized model of friction, we just say there is a coefficient of friction between the surfaces and it is independent of load, contact pressure, whatever, though it does depend on the two materials in contact.

In a slightly more detailed model, we say there is a coefficient of static friction and a coefficient of kinetic friction, but they are still constants that depend on the material pair.

In the real world, friction is a dauntingly complex problem and neither one of these idealizations is entirely accurate. For one thing, contact pressure does usually affect the coefficient of friction, but whether increasing pressure increases or decreases the coefficient depends on the exact situation. Some of the other variables that often have an effect on the coefficient of friction include surface roughness, surface flatness, lubrication, contamination, temperature, and, of course, the materials in contact.

Answer 4

Yes your right. The coefficient of kinetic / static friction is determined by the two surfaces, the condition of the two surfaces, their contact area, etc. Not the load.

Answer 5

I'm with your first 2 answers. This is something you could test at home. All you need is an adjustable incline and a box. Find the slope that is at the borderline of the box sliding. Add 3 books and repeat. To find the borderline, you might have to jostle the box at each incline setting.

Answer 6

kinetic frictions