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Calculate force of friction on car as it rolls across

  1. Jun 8, 2015 #1
    1. The problem statement, all variables and given/known data
    Calculate the force of friction on a toy car as it rolls across a flat floor.

    Given:
    mass = 0.293kg
    time = 3.66 s
    displacement = 8.7


    2. Relevant equations

    Fnet = mass x acceleration

    displacement = [(velocity1 + velocity2)/2] time

    velocity2 = velocity1 + acceleration(time)


    3. The attempt at a solution
    Step 1

    displacement = [(velocity1 + velocity2)/2] time
    v2 = (2d/time) - v1
    = 2(8.7m)/3.66s - 0m/s
    = 4.75m/s

    Step 2
    velocity2 = velocity1 + acceleration(time)
    a = v2-v1 / time
    = 4.75/3.66
    = 1.29m/s^2

    Step 3
    F=ma
    = 0.293kg x 1.29m/s^2
    = 0.38N

    so the force of friction on the car is 0.38N ?????

    I am unsure if this is right and if i have to use the Force of friction = μ x N equation
     
  2. jcsd
  3. Jun 8, 2015 #2

    billy_joule

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    The problem statement is incomplete. Please copy the entire question word for word.

    Your working implies you have more information than you've posted...
     
  4. Jun 8, 2015 #3
    Will remember to add background of the question.

    "Calculate the force of friction on your car as it rolls across a smooth level surface."

    Not sure why it says smooth level surface since there was friction between the car and the floor but...

    This is a follow up question to an experiment we did. We had to make a mousetrap car so the car was powered only by the mousetrap. The mass of my car is 0.293kg and it travelled 8.7 m in 3.66 seconds across a flat floor.
     
  5. Jun 9, 2015 #4

    billy_joule

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    Ok. The missing information is that the car comes to a stop after travelling the 8.7 metres.

    What you've done is correct.
     
  6. Jun 9, 2015 #5

    haruspex

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    Are the distance and time measured from a point where the mousetrap has ceased to supply any power?
     
  7. Jun 9, 2015 #6
    yes
     
  8. Jun 9, 2015 #7

    haruspex

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    Ok
     
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