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How fast will the car now move?

  1. Aug 8, 2014 #1
    A 100kg cart is moving at 2.3m/s. A machine has been designed to apply a force of 1200N over a distance of 0.52m as this cart passes by. How fast will the car now move?







    3. The attempt at a solution
    I used a=fnet/m where fnet was 1200-0 so the answer I got was 2307.68 m/s^2. Is this right?
     
  2. jcsd
  3. Aug 8, 2014 #2

    Nathanael

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    Why did you divide the force by the distance?

    Is newton's law "Force = distance times acceleration" or is it "Force = mass times acceleration"?


    Anyway, that gives you (if you do it correctly) the acceleration of the object, but the question didn't ask for the acceleration. You'll need to use the acceleration to find the final velocity.

    Do you know about Work and Energy? (If not, that's fine, there are other ways to solve it.)
     
  4. Aug 8, 2014 #3
    So a= 2.3m/s
     
  5. Aug 8, 2014 #4

    Nathanael

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    Look at the units. Acceleration does not have units of m/s. Acceleration has units of m/s^2


    Do you know newton's definition of force? (Also known as "Newton's Second Law")

    It says:
    Net Force = Mass times acceleration

    Therefore (if you rearrange that definition)
    Acceleration = Force divided by mass
     
  6. Aug 8, 2014 #5
    1200/100
    =12 m/s^2

    V=3.84
     
  7. Aug 8, 2014 #6

    Nathanael

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    Yes, that is correct.

    You need to explain yourself, otherwise I can't help you.
     
  8. Aug 8, 2014 #7
    I used v^2= u^2+2as
    =sqrt(2.3^2 + 2 x 12 x 0.52)
    =3.84
     
  9. Aug 8, 2014 #8
    Whoops is it 4.215
     
  10. Aug 8, 2014 #9

    Nathanael

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    Yes, that is the correct answer.
     
  11. Aug 8, 2014 #10
    Thank you!
     
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