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: Another newton law theoroy question

  1. Sep 19, 2010 #1
    1. The problem statement, all variables and given/known data

    pushing an armchair across a carpeted or at constant speed v you apply a force of 100N
    if you push same chair at constant speed 2v(twice as fast) you mush push with a force?

    3. The attempt at a solution
    newtons second law? if the net force acting on object is zero or if no force is acting on object..objects at rest will stay at rest and objects in uniform motion will stay in uniform motion in a constant velocity straight lien unless acted on by a non negative resultant force.

    ...since the speed is constant that means no force is being applied? but the initial force was 100N? and was 100N for a while until the 2v speed was reached?
  2. jcsd
  3. Sep 20, 2010 #2
    If the velocity is constant, that means that no net force is being applied. Which means that something is counteracting the 100N being applied, what force is that?

    If you double the velocity, how will that resistive force respond? (look at how the equation for that particular resistive force varies with velocity)
  4. Sep 20, 2010 #3
    It sounds like a friction problem, however I'm not sure you have given enough of the details to solve.
  5. Sep 20, 2010 #4
    Well the question is straight from the practice section of the text. That is all the info they have given.
  6. Sep 20, 2010 #5
    Yes, for this type of problem (simplicity-wise), its enough information.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook