1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Determine the force involving static coefficient

  1. Oct 29, 2015 #1
    1. The problem statement, all variables and given/known data
    A force P acts as shown on a 200kg block placed on an inclined plane. The static coefficient of friction between the block and plane are Us= 0.5 . Determine the force of P to ensure he block is in the verge of moving down. The ans given is P = 560.4 N
    i have done in 2 ways , but my ans is incorrect .... why am i wrong ?

    2. Relevant equations

    3. The attempt at a solution

    1. ) P cos 20 = Fs

    Pcos20 =0.5x9.81x200xcos10

    P= 1028N

    2. ) Wsin10 + P cos20 = 0.5x9.81x200xcos10

    Pcos20 = 0.5x9.81x200xcos10 - Wsin10

    Pcos20 = 0.5x9.81x200xcos10 – 200x9.81 sin10

    P= 665.5N

    Attached Files:

    • 002.png
      File size:
      98.7 KB
  2. jcsd
  3. Oct 29, 2015 #2


    User Avatar
    Science Advisor
    Homework Helper
    2017 Award

    What about the maximum friction if P were at 90 degrees instead of 20 ?
  4. Oct 29, 2015 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Go through the standard procedure:
    Draw the free body diagram of the block. List the forces with horizontal components, write out expressions for their values and the force balance equation. Then do the same for vertical components.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Threads - Determine force involving Date
Determining reaction forces Friday at 9:00 AM
Determine the orbital period of Phobos Feb 8, 2018
Determine the elevator's acceleration Nov 24, 2017