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!

Forces Test Redo

  1. Mar 2, 2008 #1
    Our professor is letting us redo the questions we missed on our exam for half-credit because the averages for his classes were 50, 60, and 70. I have a couple of q's I am needing help with, please.

    What is the acceleration of a 1.8 kg physics book sliding down a 36 degree incline if the coefficient of kinetic friction, uk = 0.452?

    What I have so far is Fnetx = Fg sin x (theta) - Ffk. But since Ffk is = uk x Fn, how do I find Fn? Would it be equal to Fg x cos (theta)?

    Am I headed in the right direction at all?
     
  2. jcsd
  3. Mar 2, 2008 #2

    Shooting Star

    User Avatar
    Homework Helper

    Right. You are almost there.
     
  4. Mar 2, 2008 #3
    Okay... so I got Fnetx = 3.92 N. would Fnety = 0? How would I find acceleration from that? Completely lost after this. Thanks much.
     
  5. Mar 2, 2008 #4

    Shooting Star

    User Avatar
    Homework Helper

    I don't know how you could be, after writing down the correct eqn...

    If total F is along the plane downward, then
    F = component of gravity along plane - frictional force
    = mgsin(theta) - uk*mgcos(theta).
     
  6. Mar 2, 2008 #5
    That is how i got the 3.92 N. So that is all?
     
  7. Mar 2, 2008 #6

    Shooting Star

    User Avatar
    Homework Helper

    Why, would you have liked it to be very difficult?

    The mass will cancel out, so write the eqn in symbols like I have done. That'll make it even easier and neater.

    Cheers.
     
  8. Mar 2, 2008 #7
    I just knew there had to be something else to finding the acceleration is all. Thanks much for the help.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?