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

Torque Equilibrium problem

  1. Mar 4, 2009 #1
    1. The problem statement, all variables and given/known data

    A uniform ladder of length L and mass m1 rests against a frictionless wall. The ladder makes an angle θ with the horizontal.
    (a) Find the horizontal and vertical forces the ground exerts on the base of the ladder when a firefighter of mass m2 is a distance x from the bottom. (Answer using m_1 for m1, m_2 for m2, theta for θ, g for gravity, and L and x as necessary.)

    (b) If the ladder is just on the verge of slipping when the firefighter is a distance d from the bottom, what is the coefficient of static friction between ladder and ground?

    2. Relevant equations

    Net Fy = 0
    Net Fx = 0
    Net T = 0

    3. The attempt at a solution

    I tried n_g-m_1*g-m_2*g as the answer for the vertical force because the ladder has a normal force that is exerted in reaction to the two gravitational forces from the ladder itself and the firefighter. I believe that this isn't the correct way to input it.

    for the force for horizontal I know its the frictional force minus the normal force from the wall. however I don't know how to input it using hte variables they want.
  2. jcsd
  3. Mar 5, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi vipertongn! :smile:

    Yes, the normal force will be equal and opposite to the other vertical forces.

    To find the horizontal forces, take moments about some convenient point. :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook