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Acceleration of vehicle when given torque to the wheels

  1. Dec 2, 2009 #1
    Acceleration of vehicle when given torque to the wheels....

    Ok so Im trying to figure out the acceleration of a vehicle that has a maximum of 381ft lbs of torque.With a mass of roughly 1700kg. If I use the formula f=ma, a=f/m and if I convert ft lbs to Nm its roughly 517/1700=.30m^2/s^2???

    what does meters squared/ seconds squared mean?

    then I tried F=Torque/radius, which led me to 1850/1700=1.09m/s^2??

    right now Im just throwing stuff out there, Im confused at this point, so anything to help clear this up would be great...

    Also, once I find the acceleration, I need to find the time the vehicle would take to travel 402.336meters...

    thanks sooooo much for anyone who replies.
     
  2. jcsd
  3. Dec 2, 2009 #2
    Re: Acceleration of vehicle when given torque to the wheels....

    I think some more info is needed. Is there a wheel radius?
     
  4. Dec 2, 2009 #3
    Re: Acceleration of vehicle when given torque to the wheels....

    the wheels have a radius of 0.3048meters
     
  5. Dec 2, 2009 #4
    Re: Acceleration of vehicle when given torque to the wheels....

    I think you should try doing this problem symbolically. You seem to be getting caught up using the wrong numbers and losing track of your units. Try leaving your variables as F, a, r, etc. and see if you can't find an expression for F.
     
  6. Dec 2, 2009 #5
    Re: Acceleration of vehicle when given torque to the wheels....

    do you know if im somewhat on the right track at least?
    I think im mixed up with the F/m=a units... but I dont know really how to work with the radius.... Im really trying to figure this out as quick as possible but Im trying to get another physics project done so if you could give me a hint or something to go on.
     
    Last edited: Dec 2, 2009
  7. Dec 2, 2009 #6
    Re: Acceleration of vehicle when given torque to the wheels....

    my professor said using F=ma is fine for torque but does that mean that I show torque as Nm or do I have to some how convert it to N by dividing Nm by the radius of the wheels, to use as the force?
     
  8. Dec 2, 2009 #7
    Re: Acceleration of vehicle when given torque to the wheels....

    The units of torque are force*distance. You don't convert it to force, you find the force the torque creates.

    But yes, that is the idea. Torque divided by radius of the wheels will give the horizontal force that the wheels exert on the axle, assuming the wheels don't slip on the pavement.

    Here's how I thought about it: If, at any given instant, the wheels aren't slipping, then that means the point where the wheel touches the pavement isn't moving with respect to the pavement, or with respect to us watching the car from the roadside. If that point isn't moving, it would be sensible to pick that as the pivot point. Then, the force that the wheel is exerting is Torque divided by the distance from that pivot point. There's an axle directly above the pivot, and it's a distance r away. So, torque divided by r is the forward force the axle is feeling.

    Always start by finding a good pivot point!
     
    Last edited: Dec 2, 2009
  9. Dec 2, 2009 #8
    Re: Acceleration of vehicle when given torque to the wheels....

    so I have the right idea of taking the torque/wheel radius
    which I then would divide by the mass to get the vehicle acceleration?
    Units being m/s^2?
     
  10. Dec 2, 2009 #9
    Re: Acceleration of vehicle when given torque to the wheels....

    Haha, yeah...do you really need my help with newton's 2nd? I think you can probably handle it from here.
     
  11. Dec 2, 2009 #10
    Re: Acceleration of vehicle when given torque to the wheels....

    :) Thanks man
     
  12. Dec 2, 2009 #11
    Re: Acceleration of vehicle when given torque to the wheels....

    My pleasure!
     
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