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Calculating G Forces or the Centripical force

  1. Dec 26, 2008 #1
    Hi Im brandon and Im new to this forum! Im mainly a chemistry guy and thats what Im good at in my college but I want to learn about physics too!

    How would I go about calculating the G forces or Centripical force in a vehicle in motion if I know the degree of the turn, the weight of the car, and the length of the arc?
    I need to know what units to use but to my knowledge i use Kg, M/s, and radians??
  2. jcsd
  3. Dec 26, 2008 #2
    DO I use radians as the units for the degree of the arc?

    So I have " F= ( m*v^2 ) / R "
    And for the radius I have " R= s/ theta" where theta is the angle measurement, BUT WHAT IS THE MEASUREMENT IN ? RADIANS? DEGREES?

    I got 2800 kg of force put on the side of my car which is 1.9 G forces with radians...
    mass of car- 1465
    arc length- 200 meters
    Arc angle - 90 degrees
    Speed- 35 miles an hour or 15.6 meters per second

    Can anyone tell me what i should get?
  4. Dec 26, 2008 #3


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    It's not needed. What you need is the ratio of arc length versus circumference. Knowing that there are 360 degrees in a circle, or that there are 2 [itex]\pi[/tex] radians in a circle would allow you to use either unit.

    What unit of force is equal to 1 kg m / sec^2?
    Last edited: Dec 26, 2008
  5. Dec 28, 2008 #4

    im also new here

    the law is

    theta (in radian)= lenght (of the arc)/thr redius

    theta here : is the central angle ( the measure of the arc)

    so by this law we can get the redius lenght and use it in the law

    f= m*v^2/r

    to get the centrepital force

    and from degree to raadian

    (theta in radian / the (by) constant= theta in degree/180)

    90 degree =1.57radians approximatly

    200/1.57=127.3m approxmatly

    here we can complete the problem

    that what i think
    Last edited: Dec 29, 2008
  6. Dec 28, 2008 #5


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    Force is a measure mass times acceleration which in SI units is expressed as (kg) * m/s² or N (Newtons).

    In acceleration due to a circular path like an auto on a curved roadway, the dimension of interest would be the radius of the curve as the centripetal acceleration would be expressed as v²/r. If you express your v²/r in terms of g then you can simply apply that g factor to whatever mass you may be dealing with.

    For example 60 mph on a 100 m radius curve will be

    (60*.447)² /100 = 7.2 m/s² of acceleration
    (.447 is mph to m/s conversion factor)

    divide that by 9.8 m/s² which is gravity and that = .73 g

    Then you can apply that g factor to whatever kgs of mass you have and get the force directly.
  7. Dec 28, 2008 #6


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    To determine the radius from the arc and angle you suggest use the simple relationship that there are 2π radians in a circle. (The number of radii in a circumference.)

    If a 1/4 circle is 200 m then your circumference from 90° ... 200*4 = 2π*r

    r = 800/2π = 127.32 m
    Last edited: Dec 28, 2008
  8. Dec 29, 2008 #7

    Ranger Mike

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    " F= ( m*v^2 ) / R " is correct formula
    one more piece to ponder..

    from our cone killing days in SCCA Autocross..skid pad testing ,,go to parking lot, airport,,what ever, set up circle 200 to 300 feet in diameter, drive around the cirle as fast as you can without spinning out..
    G = 1.225 x R / T squared
    R= Radius of the turn in feet
    T = Time in seconds to complete a 360 degree turn

    typical Corvette corners at .84gs
    road race sedan like Tran Am 1.15 Gs

    if you know the tire performance curve from the manufacturer charts weight (vertical load in static pound) vs Traction (lateral load in lbs) you can calculate the Cornering efficiency
    Last edited: Dec 29, 2008
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