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Friction force dilema. A new physics breakthrough? :)
Sometimes during lunch time, strange talks appear :). And then great doubts about life and physics...
Imagine two cars: one with wide tires and the other not that wide. It is obvious that the car with wider tires will curve better and brake faster, so the friction force will be greater, correct?
The friction force (Ff) is (N -> normal force; uf --> friction coeficient):
Ff = N . uf
The uf is only dependent on the material of the two surfaces, if we have a dynamic or static friction (not on the area of contact).
The N (normal force) is dependent on the gravitacional force multiplied by a coeficient that relates to the position it is being applied. For braking in a horizontal surface, you may assume that the Normal force is equal to the gravitacional force. And the gravitacional force is the mass multiplied by the gravitacional acceleration :).
My point is that today's formulas to calculate the friction force are independent on the area of the contact surface and thus wrong. They say that if we have a 1 ton car with big tires and a 1 ton car with very small tires braking or curving at 100km/h, they will have the same friction force on the tires and consequently brake within the same distance and time, and be able to curve the same way.
I believe this is wrong. I think that the friction force should be dependent on the normal force*area of contact and not just on the normal force.
So, what do you think? Am I running for the nobel prize :) or did I miss something?
Cheers,
Rui
Sometimes during lunch time, strange talks appear :). And then great doubts about life and physics...
Imagine two cars: one with wide tires and the other not that wide. It is obvious that the car with wider tires will curve better and brake faster, so the friction force will be greater, correct?
The friction force (Ff) is (N -> normal force; uf --> friction coeficient):
Ff = N . uf
The uf is only dependent on the material of the two surfaces, if we have a dynamic or static friction (not on the area of contact).
The N (normal force) is dependent on the gravitacional force multiplied by a coeficient that relates to the position it is being applied. For braking in a horizontal surface, you may assume that the Normal force is equal to the gravitacional force. And the gravitacional force is the mass multiplied by the gravitacional acceleration :).
My point is that today's formulas to calculate the friction force are independent on the area of the contact surface and thus wrong. They say that if we have a 1 ton car with big tires and a 1 ton car with very small tires braking or curving at 100km/h, they will have the same friction force on the tires and consequently brake within the same distance and time, and be able to curve the same way.
I believe this is wrong. I think that the friction force should be dependent on the normal force*area of contact and not just on the normal force.
So, what do you think? Am I running for the nobel prize :) or did I miss something?
Cheers,
Rui