Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Static Friction and Gravity

  1. Mar 31, 2010 #1
    Hey guys first time posting and I have a really frustrating question. Is there static friction when the force of gravity is pulling an object straight against a surface. I believe that there is none because (i don't know if I'm wording this right) the friction is equal to the normal of the collision. Let's say you have a 20lb object on perfectly level ground. The only forces acting on the object would be gravity and the reaction force of the ground keeping the object up. Am I right about this. Looking forward to some answers. Thanks.
     
  2. jcsd
  3. Mar 31, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

    Yes those will be the only two forces acting. Friction is only present when there is motion between them mass and the surface.
     
  4. Mar 31, 2010 #3
    Thank you so much for comfirming that. I had a really long debate with a friend about this and he refused to believe it was true. Now I know how to prove it to him. Thanks for the help.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook