Coeffincient of static friction

In summary, Kim's coffee cup needs a minimum coefficient of static friction of 0.78 in order to stay on her car's dashboard when she takes a corner with a radius of 4m and a speed of 20km/hr. This can be calculated by comparing the centripetal force needed to keep the cup in place, the normal force exerted by the cup on the dash, and the maximum force that static friction can provide based on the given mu value.
  • #1
pinkyjoshi65
260
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Kim has her coffee cup on her car's dash when she takes a corner with radius 4m and 20km/hr. What is the minimum coefficient of static friction which would aloow the coffee cup to stay there without slipping?

this is what i did, but i think it is wrong

MU= friction force/normal force= ma/mg= a/g= v^2/rg
so mu= v^2/rg= 30.80/16*9.8=0.19
 
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  • #2
pinkyjoshi65 said:
MU= friction force/normal force= ma/mg= a/g= v^2/rg
so mu= v^2/rg= 30.80/16*9.8=0.19
You equation is correct but your arithmetic is not. Did you square the r by mistake?
 
  • #3
so mu should be = v^2/rg= 30.80/4*9.8=0.78
that is the minimum coefficient of satic friction which would allow the cup to stay in postition without slipping?
 
  • #4
Yep. (If you're dealing with one of those online systems, you may want to double check the accuracy of your calculations lest you be off a bit. Redo v^2.)
 
  • #5
how do you know that it is the minimum mu and tht it will make the cup stay in position?
 
  • #6
Answer these questions:
(1) How much force is required to centripetally accelerate the cup?
(2) What normal force does the cup exert on the surface of the dash?
(3) What's the maximum force that static friction can supply for a given mu?

That should tell you the minimum mu required.
 

FAQ: Coeffincient of static friction

What is the coefficient of static friction?

The coefficient of static friction is a measurement of the amount of force required to overcome the static friction between two surfaces in contact. It is denoted by the symbol µs and is a dimensionless quantity.

How is the coefficient of static friction calculated?

The coefficient of static friction can be calculated by dividing the maximum amount of force required to overcome the static friction by the normal force acting between the two surfaces. This is represented by the equation µs = Fmax/N.

What factors affect the coefficient of static friction?

The coefficient of static friction can be affected by several factors, including the nature of the surfaces in contact, the roughness of the surfaces, the weight of the object, and the presence of any external forces acting on the object.

What is the difference between static and kinetic friction?

Static friction is the force that must be overcome to set an object in motion, while kinetic friction is the force that opposes the motion of an object that is already moving. The coefficient of static friction is typically higher than the coefficient of kinetic friction.

Why is the coefficient of static friction important?

The coefficient of static friction is important because it helps us understand the amount of force required to move an object and the stability of an object at rest. It is also crucial in determining the maximum angle at which an object can be placed on a slope without sliding down.

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