# Coefficient of static friction question

• Angelofhappiness
In summary, the conversation revolved around determining the maximum angle of a hill on which a car can be parked based on the coefficient of static friction between hard rubber and pavement. The participants discussed the relevant equations and forces involved, and suggested drawing a Free Body Diagram to solve the problem.
Angelofhappiness
Can anyone help?

The coefficient of static friction between hard rubber and normal street pavement is about 0.34. On how steep a hill (maximum angle) can you leave a car parked?

Show some work.

Thats the thing, I have no idea where to begin. I know that us = 0.34 and acceleration = 0 which means Fnet = 0 but that's all.

Angelofhappiness said:
Thats the thing, I have no idea where to begin. I know that us = 0.34 and acceleration = 0 which means Fnet = 0 but that's all.

Yes, and it is all you need to know. Which forces are acting on the car on the incline?

Angelofhappiness said:
Thats the thing, I have no idea where to begin. I know that us = 0.34 and acceleration = 0 which means Fnet = 0 but that's all.

If that is the case, you need to reread your book's chapter on this material and post your thoughts.

okay, recall that friction is the normal force times the static coefficient. You know that the car will slip when the force of the car down the hill equals the static friction. gravity causes both the normal force and the force down the incline, and these forces are perpendicular to each other, so just take some components of gravity.

Draw a Free Body Diagram of the car. Then redraw the forces acting on it in components.

## 1. What is the coefficient of static friction?

The coefficient of static friction is a dimensionless quantity that represents the amount of force required to overcome the static friction between two surfaces in contact. It is denoted by the symbol μs and is dependent on the materials and surfaces in contact, as well as the roughness and texture of the surfaces.

## 2. How is the coefficient of static friction different from the coefficient of kinetic friction?

The coefficient of static friction is the value of friction when an object is at rest, while the coefficient of kinetic friction is the value of friction when an object is in motion. The coefficient of static friction is typically higher than the coefficient of kinetic friction, as it takes more force to overcome the initial resistance of an object at rest.

## 3. How is the coefficient of static friction measured?

The coefficient of static friction can be measured experimentally by gradually increasing the force applied to an object until it begins to move. The coefficient is then calculated by dividing the maximum force required for the object to move by the normal force (force perpendicular to the surface) between the two surfaces.

## 4. What factors affect the coefficient of static friction?

The coefficient of static friction is affected by the materials and surfaces in contact, as well as the roughness and texture of the surfaces. It also depends on the weight of the object and the force applied to it. Additionally, temperature, humidity, and surface contaminants can also affect the coefficient of static friction.

## 5. How is the coefficient of static friction used in real-life applications?

The coefficient of static friction is an important factor in determining the stability and safety of objects in various situations. It is used in designing brake systems for vehicles, determining the maximum angle at which objects can be stacked without sliding, and in sports such as rock climbing to ensure a strong grip on surfaces. It is also used in building structures and determining the stability of slopes and structures.

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