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: Simple physics question. Can it be solved though?

  1. Oct 30, 2009 #1
    1. The problem statement, all variables and given/known data
    2 people. one has a mass of 125kg and pushes the other. the other travels 4m before stopping. the initial velocityof the push is 5.75m/s. Gravity is 1.67m/s2. What is the force acted on the second person.

    2. Relevant equations
    Is it even possible to figure this out without knowing the mass of the second person? (the one being pushed)

    3. The attempt at a solution
    I found the acceleration but it got me nowhere without knowing the mass of the other person.

    Thanks so much for your quick replys. I need to figure this out within the next hour. :)
  2. jcsd
  3. Oct 30, 2009 #2


    User Avatar
    Homework Helper

    Welcome to PF!

    According to Newton's third law, if A pushes on B with force F, then B pushes back on A with the same force in the opposite direction.

    So if you can find the force on one person, you've got it for the other one, too.
  4. Oct 30, 2009 #3
    Awesome. So how do I figure out the force of the first person. I have the mass (125kg) and gravity (1.67m/s2, but I'm not sure how you get the force with that. Gravity doesn't really affect the horizontal force I wouldn't think.
  5. Oct 30, 2009 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Is this really the exact wording of the question? Some things just don't make sense:

    1. What does "the initial velocity of the push" mean? Is that the initial velocity of the 2nd person? The initial velocity of the two people relative to each other? Something else?

    2. I don't believe the statement "Gravity is 1.67m/s2". Gravity is not relevant for horizontal motion, and that is not the acceleration due to gravity on the Earth. Or is this supposed to be on the moon?

    Please phrase the problem exactly as it is written, if you haven't done so here.
  6. Nov 1, 2009 #5
    I actually misread the question. It was only asking for the coefficient of friction.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook