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

Homework Help: Force Problem of normal force of the table

  1. Feb 21, 2010 #1
    1. The problem statement, all variables and given/known data
    A hand presses down on a book. Is the normal force of the table on the book larger than, smaller than, or equal to mg? (m is the book mass)

    2. Relevant equations

    3. The attempt at a solution
    I want to say the normal force is equal to mg. Am i correct?
  2. jcsd
  3. Feb 21, 2010 #2
    Wikipedia of Newton's 3rd Law:

    Whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction.

    The downward force of the book is F(weight) + F(applied by hand).
    Book acting on table.

    Now the table acting on book has the same magnitude of force but opposite direction (N3rd law). Force(normal).

    Hope that helps.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook