Question from our Lab today on Friction

[Husker70]

Homework Statement

Assuming that f=mu(N), show that the cofficient of (rolling) friction for the
car moving down the inclined plane with a constant speed is given by
mu=tan(theta) - m2/mc cos(theta)(Use symbols, not numbers.)

Homework Equations

The Attempt at a Solution

Can someone explain any of this so I can understand what they are asking.
I can't get started because I don't really understand it.
Thanks,
Kevin

 

[tiny-tim]

rolling

Hi Kevin!

(have a mu: µ and a theta: θ )

Assuming that f=mu(N), show that the cofficient of (rolling) friction for the
car moving down the inclined plane with a constant speed is given by
mu=tan(theta) - m2/mc cos(theta)(Use symbols, not numbers.)
…
Can someone explain any of this so I can understand what they are asking.
I can't get started because I don't really understand it.

hmm … fair point!

I wish professors would explain rolling more carefully.

Before I go any further, can you say what m2 and mc are (I can guess what θ is ), and show us a bit more of the question?

 

[baba89]

Sure, I'd be happy to help break down the question and provide an explanation.

First, let's define some terms and variables that are mentioned in the question:

- f: friction force
- mu: coefficient of friction
- N: normal force
- theta: angle of the inclined plane
- m2: mass of the car
- mc: mass of the car plus any additional objects it is carrying

Now, the equation given in the question is f = mu(N), which is a common formula for calculating the friction force between two surfaces. In this case, the surfaces in question are the car's tires and the inclined plane.

Next, the question asks us to show that the coefficient of friction for the car moving down the inclined plane with a constant speed is given by mu = tan(theta) - m2/mc cos(theta). To understand this equation, we need to first understand what coefficient of friction means.

Coefficient of friction is a measure of how much force is needed to overcome the friction between two surfaces. In this case, it is specifically referring to rolling friction, which is the resistance that occurs when a round object (like a car tire) rolls on a surface.

Now, let's break down the equation:

- mu = coefficient of friction
- tan(theta) = the tangent of the angle of the inclined plane
- m2/mc = the ratio of the car's mass to the combined mass of the car and any additional objects it is carrying
- cos(theta) = the cosine of the angle of the inclined plane

So, the equation is essentially saying that the coefficient of rolling friction is equal to the tangent of the angle of the inclined plane, minus the ratio of the car's mass to the combined mass of the car and any additional objects, multiplied by the cosine of the angle of the inclined plane.

This equation can be derived using principles of physics and calculus, but it may be beyond the scope of what was covered in your lab today. If you have any specific questions or are still having trouble understanding, please let me know and I'd be happy to provide further explanation.