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: Dynamics of a particle moving in a straight line question

  1. Jul 5, 2012 #1
    A car of mass 900 kg is towing a trailer of mass 300 kg along a straight horizontal road. The car and the trailer are connected by a light inextensible tow-bar and when the speed of the car is 20m s−1the brakes are applied. This produces a braking force of 2400 N. Find

    a the deceleration of the car,

    b the magnitude of the force in the tow-bar,

    c the distance travelled by the car before it stops.


    Could anyone explain to me why the tension of the car and trailer is against them? Is it because the car is decelerating?
  2. jcsd
  3. Jul 5, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    hi synkk! :smile:

    T is actually compression rather than tension (it pushes outward)

    if the towbar was a rope, then the car would decelerate but the trailer would carry on at the original speed, so they would get closer

    since that isn't happening, the towbar must be keeping them apart, so the force in it must be compression (outward) :wink:
  4. Jul 5, 2012 #3
    fast reply, thanks.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook