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Draw vectors for a car being dragged along a ramp

  1. Oct 16, 2015 #1
    1. The problem statement, all variables and given/known data

    A 1070-kg car is held in place by a light cable on a very smooth (frictionless) ramp, as shown in the figure(Figure 1) . The cable makes an angle of 31.0 ∘above the surface of the ramp, and the ramp itself rises at 25.0 ∘ above the horizontal.


    "Draw the force vectors with their tails at the front bumper of the car. The location and orientation of your vectors will be graded. The exact length of your vectors will not be graded."

    2. Relevant equations

    3. The attempt at a solution
    The problem states "a frictionless surface", so i didn't add a friction vector. Tension can only be in the cable( as far as i know?) so i put a tension vector along the cable. The weight vector i put straight down, and the normal vector perpendicular to the surface. I figured that the car is being dragged along the ramp, so i put a thrust vector along the dotted line. It looks like this as of now


    I only have two attempts remaining. I've tried a lot of different methods.. The only thing I can think of at this point is to take out the thrust vector and see if that works.
  2. jcsd
  3. Oct 16, 2015 #2

    Mister T

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    How does thrust propel a car? Is friction between the tires and the road surface involved?
  4. Oct 16, 2015 #3
    I don't know, we didn't even learn about thrust. When I go to add vectors, i can choose from thrust force, weight, tension force, normal force and friction force. I think because it says the surface is a frictionless ramp that I shouldn't include the friction force..I already tried taking the thrust vector out and that was wrong too. i feel like im out of viable options?
  5. Oct 16, 2015 #4

    Mister T

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    Uhhh... When you say "we" do you really mean "I"? You really don't know what force propels a car, and you don't know if friction has anything to do with it?

    It looks like ##\vec{T}## is not quite at the right angle. I don't know if that's the problem.
  6. Oct 16, 2015 #5
    I mean in the class, we didn't go over thrust. Sorry lol. Well a normal car it would be related to the engine, this car is being held by the cable. Actually, because the car isn't moving, is there no thrust at all?
  7. Oct 18, 2015 #6


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    Thrust is just another word for force, though it is usually reserved for a push rather than a pull, and specifically for the driving force produced by an engine.
    As you say, the car is merely being held in place, so the three forces you described initially are all there are. Since the ramp is frictionless, the car has no means of producing a thrust anyway.
  8. Oct 18, 2015 #7

    Mister T

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    And that, not the fact that the car is motionless, is the reason why the thrust is zero.

    Think about a drag race between a Ferrari and a Civic. The Civic is on dry pavement and the Ferrari is on wet ice.
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