Coefficient of static & kinetic friction

In summary, to find the coefficient of static friction, you can use the formula u = f/N, where f is the force needed to start the motion of the object and N is the normal force. In this case, the coefficient of static friction is 0.2. The problem asked for the coefficient of static friction because in order to move an object, you need to overcome the static friction.
  • #1
ffrancis
11
0

Homework Statement


If the force needed to start the motion of an object having a mass of 2.5 kg is 4.90 N, what is the coefficient of static friction?

Homework Equations


f = uN
Since u is missing, the formula is u = f/N

The Attempt at a Solution


u = 4.90 N/(2.5 kg X 9.8 m/s2)
u = 4.90 N/24.5 N
u = 0.2

The problem is asking for the coefficient of static friction. I'm not sure if I got the answer for kinetic friction? I know the difference between the two but I don't know why the problem required static friction when it is talking about a moving object.
 
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  • #2
When an object is at rest it will have static friction and kinetic friction when it is moving. So in order to move an object, you will need to overcome the static friction.
 
  • #3
semc said:
When an object is at rest it will have static friction and kinetic friction when it is moving. So in order to move an object, you will need to overcome the static friction.

Thanks semc. But is my solution correct?
 

Related to Coefficient of static & kinetic friction

What is the coefficient of static friction and how is it calculated?

The coefficient of static friction is a value that represents the amount of force required to overcome the static friction between two surfaces in contact. It is calculated by dividing the maximum force of static friction by the normal force between the two surfaces. The formula is μs = Fmax / Fn.

What is the difference between coefficient of static friction and coefficient of kinetic friction?

The coefficient of static friction is the value that represents the amount of force required to overcome the static friction between two surfaces in contact when they are at rest. On the other hand, the coefficient of kinetic friction is the value that represents the amount of force required to keep two surfaces in motion at a constant velocity. The coefficient of kinetic friction is usually lower than the coefficient of static friction.

How does the coefficient of static friction affect the motion of objects?

The coefficient of static friction plays a crucial role in determining the motion of objects. If the coefficient of static friction is high, it means that more force is required to overcome the static friction, making it difficult for the object to start moving. On the other hand, if the coefficient of static friction is low, it means that less force is needed to overcome the static friction, making it easier for the object to start moving.

What factors can affect the coefficient of static friction?

The coefficient of static friction can be affected by several factors, including the texture of the surfaces in contact, the weight of the object, and the presence of any lubricants or contaminants on the surfaces. Additionally, the coefficient of static friction can also vary depending on the environmental conditions such as temperature and humidity.

How can the coefficient of kinetic friction be measured?

The coefficient of kinetic friction can be measured by conducting experiments where the force required to keep an object in motion at a constant velocity is measured and compared to the normal force between the two surfaces. Another method is to use an instrument called a tribometer, which can directly measure the coefficient of kinetic friction between two surfaces.

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