Coefficient of Sliding Friction

[vitaly]

Does anybody know a website that gives sliding friction (blocks on planes, etc.) example problems? I am trying to figure out how to calculate the coefficient of sliding friction, but I'm having problems doing so.

I know the general equation is:
coefficient of sliding friction = friction force of motion / normal force.

My questions are:
1) Is the normal force just the mass of the object that is sliding?
2) What exactly is the "friction force of motion"?
3) Can anybody include an example problem to find the coefficient of sliding friction?

Thanks for all the help.

 

[JFo]

1) The normal force comes about when two surfaces are in contact with each other, the normal force is always perpendicular to the surface. (The friction can be thought of as the component of force from contact that is parallel to the surface.)

2) The frictional force of motion is actually very hard to define. It occurs due to the interactions between the molecules of the two surfaces in contact. It always acts to oppose the direction of motion on an object.

3) Do a search on this forum for friction, and I'm sure you'll find a ton of examples.

 

[thepatientmental]

Hi there,

I can recommend a few websites that provide example problems for calculating the coefficient of sliding friction.

1) Khan Academy has a video lesson and practice problems on calculating the coefficient of sliding friction: https://www.khanacademy.org/science...efficient-of-sliding-friction-example-problem

2) The Physics Classroom also has a lesson and practice problems on this topic: https://www.physicsclassroom.com/cl...lculating-the-Coefficient-of-Sliding-Friction

3) The University of British Columbia's Physics and Astronomy department has a webpage with a few example problems and solutions for calculating the coefficient of sliding friction: https://www.phas.ubc.ca/~michal/202/lecture13.pdf

To answer your questions:

1) The normal force is not just the mass of the object, but rather the force that the surface exerts on the object perpendicular to the surface. In most cases, this force will be equal to the weight of the object.

2) The friction force of motion is the force that opposes the motion of the object and is caused by the interaction between the two surfaces in contact. This force is what we are trying to calculate in order to find the coefficient of sliding friction.

3) Here is an example problem: A block with a mass of 10 kg is placed on a rough horizontal surface. When a force of 50 N is applied to the block, it starts moving with a constant velocity. The coefficient of sliding friction between the block and the surface is 0.3. What is the normal force acting on the block and what is the friction force of motion?

Solution:
To find the normal force, we can use the equation F = ma, where F is the net force acting on the block, m is the mass of the block, and a is the acceleration (which is 0 since the block is moving at a constant velocity).
Therefore, the normal force is equal to the weight of the block, which is 98 N (10 kg x 9.8 m/s^2).

To find the friction force of motion, we can use the equation F = μN, where μ is the coefficient of sliding friction and N is the normal force.
Substituting the values, we get F = 0.3 x