# Kinetic or Static coefficient?

• wakejosh
In summary, the question is asking for the force of friction between a car's tires and an icy road while the car is sliding. The correct answer would be c, less than the normal force of the road times the coefficient of kinetic friction. The person asking the question also wonders if the coefficient of static friction should be used instead, but the expert clarifies that kinetic friction is the correct choice in this scenario.
wakejosh
I have this question on my homework, but I think maybe all the answers are wrong. I figure it should be C since the road is icy, but shouldn't I be using the coefficient of static friction instead of kinetic? any help is appreciated. thanks.

As a car skids with its wheels locked trying to stop on a road
covered with ice and snow,
the force of friction between the icy road and the tires will
"normal" and "perpendicular" have the same meaning)

a. greater than the normal force of the road times the coefficient
of static friction
b. equal to the normal force of the road times the coefficient of
static friction
c. less than the normal force of the road times the coefficient of
kinetic friction
d. greater than the normal force of the road times the coefficient
of kinetic friction
e. equal to the normal force of the road times the coefficient of
kinetic friction.

thje way the question is worded means there is friction between the tires and the icy road regardless of the ice

how do you calculate force of friction?? Is there any OTHER way that you know of?

Let's see... the car is sliding along the ice, so it's actually moving. Which friction would you use if an object is sliding a surface?

This is a case of kinetic friction.
The static friction only applies to a rotating wheel (the friction between the wheel and the road allow the wheel to rotate); since it is only skidding, kinetic friction is the right one.

## 1. What is the difference between kinetic and static coefficient?

The kinetic coefficient of friction is a measure of the resistance between two surfaces in motion, while the static coefficient of friction is a measure of the resistance between two surfaces at rest. In other words, the kinetic coefficient applies when there is movement between the surfaces, while the static coefficient applies when there is no movement.

## 2. How do you calculate the kinetic and static coefficients?

The kinetic coefficient of friction is calculated by dividing the force required to keep an object in motion by the normal force between the two surfaces. The static coefficient of friction is calculated by dividing the force required to start an object in motion by the normal force between the two surfaces.

## 3. What factors affect the values of kinetic and static coefficients?

The values of kinetic and static coefficients can be affected by several factors, including the nature of the surfaces in contact, the roughness of the surfaces, the temperature, and the presence of any lubricants or contaminants between the surfaces.

## 4. Why is it important to know the values of kinetic and static coefficients?

The values of kinetic and static coefficients are important in understanding the behavior of objects in motion and at rest. They can help engineers determine the amount of force needed to move an object or keep it in motion, and they are also crucial in designing structures and equipment that need to withstand frictional forces.

## 5. How can the values of kinetic and static coefficients be used in real-world applications?

The values of kinetic and static coefficients have numerous real-world applications, such as in designing tires for different road surfaces, developing brakes for vehicles, and determining the stability of structures in earthquake-prone areas. They are also used in sports equipment design, such as in determining the appropriate coefficient of friction for different types of sports shoes on different playing surfaces.

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