Register to reply 
Finding force of friction 
Share this thread: 
#1
Nov2310, 08:06 PM

P: 38

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


#2
Nov2310, 09:14 PM

Sci Advisor
HW Helper
PF Gold
P: 6,041

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
Nov2310, 09:44 PM

P: 38

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
FappFfrict = 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
Nov2310, 10:14 PM

Sci Advisor
HW Helper
PF Gold
P: 6,041

Finding force of friction



#5
Nov2310, 11:05 PM

P: 38

Oh true, didn't even think about it. Ha.
Thank you , appreciate it. 


Register to reply 
Related Discussions  
Finding min/max force (net force sliding friction problem)  Introductory Physics Homework  3  
Finding the force of friction acting on an object  static or kinetic friction?  Introductory Physics Homework  1  
Finding force of friction with only applied force and acceleration given?  Introductory Physics Homework  1  
Finding a Vertical Force given friction and a horizontal force  Introductory Physics Homework  4  
Help finding force of friction  Introductory Physics Homework  0 