Need help finding coefficient of kinetic friction

In summary, to find the coefficient of kinetic friction between a packing crate and a rough horizontal surface, a horizontal force of 150 N is used to push a 40.0 kg crate a distance of 6.00 m at constant speed. Using the equation Fy= -mgy + N, the normal force is found to be 392 N. Since the resultant force is zero at constant speed, the frictional force is also 150 N. Thus, the coefficient of kinetic friction is calculated to be 0.38.
  • #1
zinniagirl
3
0

Homework Statement


A horizontal force of 150 N is used to push a 40.0 kg packing crate a distance of 6.00 m on a rough horizontal surface. If the crate moves at constant speed, find the coefficient of kinetic friction between the crate and the surface.


Homework Equations


fK= coeff. of kin. friction X N
Fy= -mgy + normal force


The Attempt at a Solution


I started by using Fy= -mgy + N to be 0= -40 (9.8) (cos 0) + N and found N be 392. But now I'm not sure where to go from here to find the coefficient of kinetic friction. Can anyone help?
 
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  • #2
Constant speed means the resultant force is zero...so what is the value of the frictional force?
 
  • #3
rock.freak667 said:
Constant speed means the resultant force is zero...so what is the value of the frictional force?

150 N. So the coefficient of kinetic friction would then be .38, correct?
 
  • #4
Yes that should be correct.
 
  • #5
Thanks!
 

1. What is the coefficient of kinetic friction?

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

2. How is the coefficient of kinetic friction calculated?

The coefficient of kinetic friction can be calculated by dividing the force of kinetic friction by the normal force between the two surfaces. It can also be determined experimentally by measuring the force required to keep an object moving at a constant velocity.

3. What factors affect the coefficient of kinetic friction?

The coefficient of kinetic friction is affected by several factors, including the nature of the two surfaces in contact, the roughness of the surfaces, and the presence of any lubricants or contaminants. The normal force and the speed of motion also play a role in determining the coefficient of kinetic friction.

4. Why is it important to determine the coefficient of kinetic friction?

Knowing the coefficient of kinetic friction is important in many fields, including engineering and physics. It helps in understanding the forces involved in motion and designing systems that minimize frictional losses. It is also crucial in predicting the behavior of objects sliding or rolling on surfaces.

5. How can I find the coefficient of kinetic friction for a specific material?

The coefficient of kinetic friction for a specific material can be found in reference tables or by conducting experiments. It is also possible to estimate the coefficient of kinetic friction by comparing the material to other known materials with similar properties. Ultimately, the most accurate way to determine the coefficient of kinetic friction is through experimentation.

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