1. Not finding help here? Sign up for a free 30min 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!

What is the magnitude of the force?

  1. Nov 13, 2008 #1
    A 184-kg crate is being pushed across a horizontal floor by a force P that makes an angle of 15.2 ° below the horizontal. The coefficient of kinetic friction is 0.264. What should be the magnitude of P, so that the net work done by it and the kinetic frictional force is zero?

    Ok so this is what Ive come up with...

    w=mg= (184)(9.8) = 1803.2 N

    Fk= Uk * Fn = (.264)(1803.2) = 476.05

    Fn equals w (but opposite, right?

    Then...

    Fnet of y = 0

    Fnet of x = Pcos(15.2) - Fk = 0

    so...

    P = 476.05 / cos(15.2) = 493.30 N.



    But Im told thats the wrong answer!! Why??? Please help me!

    Thank you!
     
  2. jcsd
  3. Nov 14, 2008 #2

    Redbelly98

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    The normal force is not simply equal to the weight, since P has a downwards component.

    Have you drawn a freebody diagram? That's the best way to see all forces involved.
     
  4. Nov 14, 2008 #3
    The push force is partially up and partially sideways. The up part of the force counteracts some of the gravity force and changes the normal force.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: What is the magnitude of the force?
Loading...