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!

Finding velocities in F vs x graph

  1. Jun 23, 2010 #1
    1. The problem statement, all variables and given/known data
    A object of mass 3.00 kg is subject to a force Fx that varies with position as in the figure below.

    Find the work done by the force on the object as it moves as follows:
    (a) from x = 0 to x = 4.00 m
    (b) from x = 5.00 m to x = 10.0 m
    (c) from x = 11.0 m to x = 15.0 m.
    (d) If the object has a speed of 0.500 m/s at x = 0, find:
    speed at x = 5.00 m
    speed at x = 15.0 m

    3. The attempt at a solution
    a. W=2.5N (4m) / 2 = 5J
    b. W=3N (5m) = 15J
    c. W=2.5N (4m) / 2 = 5J
    d. W=1/2 mv2 - 1/2 mvo2

    x=5m 15J = 3kg v - (3kg)(0.500m/s)
    v=2.29 m/s

    x=15m 0=3kg v - (3kg)(0.500m/s)
    v=0.5 m/s
    Last edited: Jun 23, 2010
  2. jcsd
  3. Jun 23, 2010 #2


    User Avatar
    Homework Helper
    Gold Member

    I would not use 2.5 N for the force. I suggest that you find an equation for the straight line in the form F = mx and calculate the force at 5 m.
    Looks good.
    Same comment as part (a)
    What happened to the 1/2 and the square of the speed in the expressions above?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?