1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Coefficient of static friction of a sliding box

  1. Mar 14, 2014 #1
    1. The problem statement, all variables and given/known data

    A box rest on an incline making a 34 angle with the horizontal. It is found that a parallel force to the incline of at least 235 N can prevent the box from sliding down the incline. If the weight of the box is 800 N, find the coefficient of static friction between the box and the incline.

    2. Relevant equations

    Just wanted to know what formula to use or at least how construct the formula.


    3. The attempt at a solution

    Didn't know where to start.
     
  2. jcsd
  3. Mar 14, 2014 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    Hi DB91. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    You are not needing a formula yet! The first step is to draw a clear, neat diagram, to mark on everything you know here.

    Post that when you've done it. :wink:
     
    Last edited by a moderator: May 6, 2017
  4. Mar 14, 2014 #3
    https://mail.google.com/mail/u/0/?ui=2&ik=d83d1b3b4d&view=att&th=144c131a0bf54f59&attid=0.1&disp=emb&realattid=ii_144c1315a9dabb9a&zw&atsh=1
     
    Last edited by a moderator: May 6, 2017
  5. Mar 14, 2014 #4
    Would it be: (800×9.8 sin⁡34)/235 = f
     
  6. Mar 14, 2014 #5

    NascentOxygen

    User Avatar

    Staff: Mentor

    Your image doesn't show up. (I doubt that that is a link to an image, anyway.)
     
  7. Mar 14, 2014 #6
    I'll try a different address

    Untitled.png
     
    Last edited: Mar 14, 2014
  8. Mar 14, 2014 #7

    NascentOxygen

    User Avatar

    Staff: Mentor

    Your image is accessible now. (I think you have included a lot of whitespace in it?)

    The question refers to an arrangement of forces needed "to prevent the box from sliding down" the incline. So this tells you the direction in which friction will be acting in your forces diagram. So, in what direction will friction be acting here, and why have you decided it must be in this direction?
     
  9. Mar 14, 2014 #8
    The friction force would be acting in the opposite direction of the force applied on the box. Right?
     
  10. Mar 14, 2014 #9

    NascentOxygen

    User Avatar

    Staff: Mentor

    Not necessarily. It depends on what the applied force is tending to do.

    How could you work out the correct answer to this?
     
  11. Mar 14, 2014 #10
    (800×9.8 sin⁡34)/235 = f...?

    Sorry physics is defiantly not one of my strong points.
     
  12. Mar 15, 2014 #11

    NascentOxygen

    User Avatar

    Staff: Mentor

    Well, if the box were sitting stationary on the incline, and needed no extra external force to keep it steady, what direction would you be drawing the arrow showing the friction force that is acting on the block?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted