# Homework Help: How can you determine the normal force?

1. Oct 7, 2008

### davidelete

1. The problem statement, all variables and given/known data
The diagram below shows the forces acting on a block moving at a constant velocity down an inclined plane. The weight of the block, Fw, can be resoled into two components, one parallel to the surface of the plane, Fll, and one perpendicular to the surface of the plane, F_l_. If you know the weight of the block and the value of angle θ when the block moves at constant velocity, you can calculate the coefficient of sliding friction. You can also use a computer to do the calculations for you.

http://img352.imageshack.us/img352/5617/physicstrianglethingac9.png [Broken]

1. What are the two forces the values of which must be known before the coefficient of sliding friction can be calculated?

2. What data must you have in order to determine these two forces?

3. How can you determine the normal force?

4. How can you determine the force of friction?

5. What equation is used to calculate the coefficient of sliding friction?

6. In the space below, draw a flowchart to calculate the coefficient of sliding friction.

7. If you have access to a computer, follow your flowchart and write a computer program to calculate the coefficient of sliding friction. The measure of angle θ must be expressed in radians. Let Ff represent the force of friction, and FN represent the normal force. Attach a printout of your program to this page.

8. Choose a weight between 25 N and 74 N and an angle θ between 15° and 30°. Enter these data and run your program. Attach a printout of your results to this page.

9. After you have run several different values for θ, try to determine a relationship between the coefficient of friction and trig functions of angle θ.

2. Relevant equations
N/A as of now. I first have to figure out the first few before I get into any sort of math.

3. The attempt at a solution

1. Frictional Force (Ff)and Normal Force (FN)

2. The weight of the box, gravity, and the degree of θ.

3. Multiply the mass by negative gravity as in FN.
My teacher said something about the cosine of θ, but I don't really know how to implement this, being that this is the first day that we are going over vectors and she bombarded us with this.

4. The force of friction can be determined by normal force as in Ff=μ* FN

5. Ff=μ* FN or μ=Ff/FN

6. I have no idea. My teacher just said to put our problem solving steps down for this one. First I need some problem solving steps...

7. She said to use Microsoft Excel for this purpose. As soon as I figure out the first five, this shouldn't be too hard. Any guidance would help, of course.

8. ???

9. ???
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: May 3, 2017
2. Oct 7, 2008

### barato

Hmmmmm. Ill try to work it out, I am also just beginning physics. Ill tell you what I got.

3. Oct 7, 2008

Help!!!

4. Oct 7, 2008