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!

Quick work question.

  1. Aug 1, 2007 #1
    I'm working on some work problems.

    Let's say we're moving an item up a 20* incline. It's mass is 150kg. The friction coefficient is .20.

    Can gravity and/or normal forces "do" work?

    Also, how does one calculate the minimum amount of force required to move this object at a constant speed?
    Last edited: Aug 1, 2007
  2. jcsd
  3. Aug 1, 2007 #2
    Normal forces act in a direction perpendicular to the contact point on the plane. If you're talking about moving an object along a plane, the normal force can do no work since it's perpendicular to the object's direction of motion.

    In this situation, however, gravity CAN do work. If you are moving the object up, against the force of gravity, gravity is doing negative work on the object.

    Constant speed means no acceleration. By Newton's second law, if a = 0 then F = 0 also. Thus, to find the conditions for constant speed, you find the situation in which the total net force on the object is 0 (all forces cancel one another).
  4. Aug 1, 2007 #3
    Well for gravity, I did:


    Is that correct?
  5. Aug 1, 2007 #4
    Only if you move it along the plane a distance of 1 meter. You know from trig that your height would be d*sinθ where d is the distance along the plane and θ is the angle of inclination of the plane. Other than that, it's right!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Quick work question.
  1. Quick work question (Replies: 10)