How to Find Coefficient of Friction on Sandpaper Using Applied Force and Mass?

In summary, the protagonist is having trouble trying to find the coefficient of friction for a block of wood that is being held down by a spring scale. He has tried using different masses and applied forces, but has been unsuccessful. He has been told by a tutor that if he can find the force of friction, he can solve the equation for the applied force. However, he has not been able to find the coefficient of friction for a block of wood that is moving slowly.
  • #1
Havenater23
38
0

Homework Statement


I have a lab project in physics and I'm having a bit of trouble. We measured the Applied force of a moving block of wood using a spring scale. The first trials were don't with just the table , knowing the mass and applied force I was able to find the friction force; simply it was the same as F app. My problem now is that we did other trials on sandpaper, and I have the Applied force and mass and I don't know how to find the mass. We are suppose to find the Co efficent of friction, but not through math ; we have to use a graph where : y = mx aka Ff=U*Fn

Which isn't too bad, I just can't figure out how to get Force friction with only the mass and applied force when it is using the sand paper.

Mass = 0.27952 kg Force applied = 2.0N
Fn = Fg
mg= 0.27952(9.8)= 2.739296 N

Help please


Homework Equations





The Attempt at a Solution

 
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  • #2
I am assuming that the block or mass is moving slowly or at constant speed when the force is applied...in the 2nd example, you know the applied force so you then know the kinetic friction force, and since you have calculated the normal force, plot that point on the graph with Ffriction on the y-axis and the normal force on the x axis. Then try another mass, and do the same, moving it slowly; and yet another...your graph should approximate a straight line, the slope of which is____?
 
  • #3
Can't find friction, yes I have the Force normal , but no coefficient. Even if I know the applied force I don't know how that helps me find friction example


Fapp-Ffrict = MA


I only know F app and mass



Ffrict = U * Fn

Don't see how you solve unless Fapp in the 2nd problem also equals Ffrict.
 
  • #4
Havenater23 said:
Can't find friction, yes I have the Force normal , but no coefficient. Even if I know the applied force I don't know how that helps me find friction example


Fapp-Ffrict = MA


I only know F app and mass



Ffrict = U * Fn

Don't see how you solve unless Fapp in the 2nd problem also equals Ffrict.
That's right, and that is why i mentioned that in your experiment, you move the object slowly so it doesn't accelerate (a =0). Then Fapp-Ffrict = 0, or Fapp = ffrict. If you use too much of a force and the object accelerates, now you need a means of determining the acceleration. Instead, move it s-l-o-w-l-y, without accelerating. Per Newton 1, an object at rest or moving in a straight line at constant speed, will remain at rest or moving in a straight line at constant speed, unless the net force acting on it is greater than 0. Keep it at constant speed, and F_net = 0.
 
  • #5
Oh true, didn't even think about it. Ha.

Thank you , appreciate it.
 

1. What is friction?

Friction is a force that opposes the motion of two surfaces that are in contact with each other. It is caused by the microscopic irregularities on the surface of objects that come into contact.

2. How is the force of friction calculated?

The force of friction can be calculated by multiplying the coefficient of friction (which depends on the materials in contact) by the normal force (which is the force exerted by one object on another).

3. What factors affect the force of friction?

The force of friction can be affected by the types of surfaces in contact, the roughness of the surfaces, the normal force, and the presence of any lubricants.

4. How does the force of friction affect motion?

The force of friction can either help or hinder motion. In some cases, friction can provide the necessary force to move an object, such as with car tires on a road. In other cases, friction can slow down or stop motion, such as when walking on a slippery surface.

5. How can the force of friction be reduced?

The force of friction can be reduced by using lubricants, such as oil or grease, between two surfaces. Additionally, using smoother or more slippery surfaces, such as ice or polished metal, can also reduce friction.

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