1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Pulling on a rope attached to a box: Newton's Laws and Incline Planes

  1. Oct 2, 2011 #1
    1. The problem statement, all variables and given/known data

    A student decides to move a box of books into her dormitory room by pulling on a rope attached to the box. She pulls with a force of 130.0 N at an angle of 15.0° above the horizontal. The box has a mass of 25.0 kg, and the coefficient of kinetic friction between box and floor is 0.300.
    (a) Find the acceleration of the box.

    (b) The student now starts moving the box up a 10.0° incline, keeping her 130.0 N force directed at 15.0° above the line of the incline. If the coefficient of friction is unchanged, what is the new acceleration of the box?

    2. Relevant equations

    F=ma, Assorted equations derived from Newton's Laws

    3. The attempt at a solution

    I found the answer to part A to be 2.483572006 m/s/s. In part B, I attempted to determine the forces affecting the situation: rope tension, weight, normal force, and frictional force. I think I get lost trying to find these forces.

  2. jcsd
  3. Oct 2, 2011 #2


    User Avatar

    Staff: Mentor

    You will get lost if you don't draw a large diagram. Maybe a couple, as you discard the first when you realize you've marked some things incorrectly. As before, the rope takes some of the "weight", reducing the force the block exerts normal to the incline and thus reducing the force to overcome friction.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook