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: Calculating Net Force results in a final velocity

  1. Jan 14, 2015 #1
    1. The problem statement, all variables and given/known data

    As simple as the question may seem, I require some honest help. I'm particularly new to physics.

    The question is the following:
    A net force of magnitude 4.0N acts on a body of mass 3.0kg for 6.0 s. The body is initially at rest.
    Which of the following is the speed of the body after the 6.0s interval?

    2. Relevant equations

    a = Fnet / m
    Fnet = m • a
    1 Newton = 1 kg • m/s^2

    3. The attempt at a solution

    I came across this question while browsing some IB tests online for High Level physics and decided to try to solve some of them. Looking at this one, I researched the equations necessary but can't find out how to calculate a net force using only force exerted, mass, and time. On the other hand, I can solve it with both mass and acceleration.
    Any tips or equations I haven't found yet? Thank you.
  2. jcsd
  3. Jan 14, 2015 #2
    Doesn't the problem statement say that the net force is 4 N?

  4. Jan 15, 2015 #3
    Sorry, it's asking for the speed of after 6 seconds.
  5. Jan 15, 2015 #4


    User Avatar

    Staff: Mentor

    What is the equation of motion for constant acceleration that relates the velocity to the acceleration and the time? You didn't list it in your Relevant Equations...
  6. Jan 15, 2015 #5
    So what's the acceleration?
  7. Jan 15, 2015 #6
    Honestly, I don't know. The question only offers me a time, mass, and exerted force.
  8. Jan 15, 2015 #7
    Most likely because I don't know it.
  9. Jan 15, 2015 #8


    User Avatar

    Staff: Mentor

    You are showing *very* little effort here. Write out the kinetic equations of motion for constant acceleration for us. That is the best starting point. And you already wrote the equation relating Force, Mass and Acceleration in your first post. So you do too know how to calculate the acceleration. You get these equations from your textbook (most likely your current chapter), and/or you can look them up at wikipedia or Hyperphysics.
  10. Jan 15, 2015 #9
    In support of what Berkeman said, what does the equation

    a = Fnet / m

    mean to you? You wrote it down as one of your relevant equations.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook