Coefficient of kinetic friction forces

In summary, to find the applied force for an object with a coefficient of kinetic friction of 0.30 and an acceleration of 5m/s^2, you must first draw a force diagram and identify all the forces acting upon the object, including the applied force, friction force, normal force, and gravitational force. Then, calculate the y-component and x-component of the net force to determine the applied force.
  • #1
yoyo16
35
0

Homework Statement



Find the applied force for a object if the coefficient of kinetic friction equals 0.30 and the acceleration equals 5m/s^2. The applied force makes a 40 degree angle with the horizontal. The mass of the object is 10kg.

Homework Equations


Fnet=ma


The Attempt at a Solution


Ff=(0.3)(10)(9.8)=29.4
(coefficient)(normal force=mg)

Fnet =Facos40-29.4
Fnet=ma
ma=Facos40-29.4
Fa=103.6

I don't know if I did this right. Can someone please explain to me how to do this correctly. Thanks!
 
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  • #2
yoyo16 said:

The Attempt at a Solution


Ff=(0.3)(10)(9.8)=29.4
(coefficient)(normal force=mg)


If I understand the question correctly, the above is not correct. That is, normal force does not equal mg in this case, rendering the rest of your calculations incorrect.

I'd start by drawing a force diagram and clearly labeling ALL the forces acting upon the object.
 
  • #3
So how would you find out the friction force without knowing the normal force?
 
  • #4
Draw a force diagram. The problem states that the applied force makes a 40 degree angle with horizontal. Draw that force vector, along with friction force, normal force and gravitational force.

After doing so, figure out the y-component and x-component of the net Force. Start with the y-component. What are all the upward and downward forces acting upon the object?
 
  • #5


Your attempt at the solution is correct. The coefficient of kinetic friction (0.3) tells us that the force of friction is 30% of the normal force (29.4 N in this case). The applied force (Fa) can be found by using the formula Fnet = ma, where Fnet is the net force, m is the mass of the object, and a is the acceleration. In this case, the net force is equal to the applied force (Fa) minus the force of friction (29.4 N). By rearranging the formula, you can solve for Fa, which is equal to 103.6 N. This means that in order to achieve an acceleration of 5 m/s^2 for an object with a mass of 10 kg, an applied force of 103.6 N is needed, at a 40 degree angle with the horizontal. This solution is correct and follows the correct steps to solve for the applied force.
 

What is the coefficient of kinetic friction?

The coefficient of kinetic friction is a measure of the resistance between two surfaces in contact when one is in motion relative to the other. It is represented by the symbol μ and is a dimensionless quantity.

How is the coefficient of kinetic friction calculated?

The coefficient of kinetic friction is calculated by dividing the force of kinetic friction by the normal force between the two surfaces. Mathematically, it can be represented as μ=Fk/N, where μ is the coefficient of kinetic friction, Fk is the force of kinetic friction, and N is the normal force.

What factors affect the coefficient of kinetic friction?

The coefficient of kinetic friction is influenced by several factors including the nature of the surfaces in contact, the roughness of the surfaces, the amount of force applied, and the presence of any lubricants or other substances between the surfaces.

What is the difference between static and kinetic friction?

Static friction is the resistance between two surfaces in contact when there is no relative motion between them. Kinetic friction, on the other hand, is the resistance between two surfaces in contact when one is in motion relative to the other. The coefficient of static friction is typically higher than the coefficient of kinetic friction.

Why is the coefficient of kinetic friction important?

The coefficient of kinetic friction is an important concept in physics and engineering as it helps to determine the amount of force needed to move an object along a surface. It is also used in designing and optimizing various machines and structures where friction is a key factor.

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