
#1
Dec1207, 03:34 PM


#2
Dec1207, 03:41 PM

Mentor
P: 40,876

The object begins to slide when there's a net force acting down the incline. What are the components of the weight? Are you given the coefficient of friction? How can you calculate the maximum value of static friction?




#3
Dec1207, 03:43 PM

P: 19

All I was given was the mass of the object




#4
Dec1207, 03:47 PM

Mentor
P: 40,876

Overcoming Friction
The mass is one piece of data that you don't need.




#5
Dec1207, 03:56 PM

P: 19

Well, we had to predict at what height the object would move, and all we were given was the mass. We were not aloud to raise the board. Tho we were aloud to measure the lenght of the board, which was 91.5cm long.




#6
Dec1207, 03:58 PM

P: 19

and wouldn't you need the mass to find the force of gravity, and from there you could find the force of friction and the natural force.




#7
Dec1207, 03:59 PM

Mentor
P: 40,876

If you knew the coefficient of friction, you could calculate the angle the board must have for the object to start sliding. I suggest you do that and then estimate (or guess) the coefficient of friction for this material against wood.




#8
Dec1207, 04:01 PM

Mentor
P: 40,876





#9
Dec1207, 04:06 PM

P: 19

what is a coefficient of friction?




#10
Dec1207, 04:13 PM

Sci Advisor
P: 2,283





#11
Dec1207, 04:13 PM

P: 19

Here is my force diagram
I'm trying to figure out how to tell when the friction force has decreased enough for the object to move. 



#12
Dec1207, 04:19 PM

Sci Advisor
P: 2,283

Like DocAl said, you'll have to estimate the coefficient of static friction since it was not given.
Here are some typical values: http://www.engineershandbook.com/Tab...efficients.htm Then you can use the length of the board to find the height required to get the object to slide. This experiment involves some assumptions so it's probably the concept that they want you to learn and not an exact value for height. That is to say that they want you to realize that the mass of the object is not related to the coefficient of friction. 



#13
Dec1207, 04:22 PM

P: 19

so how would i use the coefficient of friction to figure out the height?




#14
Dec1207, 04:25 PM

Sci Advisor
P: 2,283

Hint: Coefficient of static friction = tan(x)
where, x = the angle of the incline relative to the x axis. 



#15
Dec1207, 04:28 PM

P: 19

ok, i get that now. But is there a formula to determine when the static friction will become kinetic friciton? or is that the level at which the friction turns into kinetic?




#16
Dec1207, 04:31 PM

Sci Advisor
P: 2,283





#17
Dec1207, 04:35 PM

P: 19

ok, i'll try to work it all out



Register to reply 
Related Discussions  
Overcoming friction problems  Introductory Physics Homework  4  
Finding the force overcoming friction  Introductory Physics Homework  1  
[SOLVED] Overcoming friction and then some.  Introductory Physics Homework  6  
One more problem.. overcoming friction  Introductory Physics Homework  0 