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How to calculate the distance travelled in work and energy?

  1. Apr 22, 2015 #1
    1. The problem statement, all variables and given/known data

    A body of mass 8.0 kg is initially at rest on a horizontal frictionless surface. A
    force of 18 N acts on it and accelerates it to a final velocity of 12 m/s. Calculate
    (a) the distance travelled,
    (b) the work done by the force,
    (c) the final KE of the body,

    2. Relevant equations
    NONE

    3. The attempt at a solution

    (a): x=7.35
    (b) W= 132.3 J
    (c) KE= 48 J
     
  2. jcsd
  3. Apr 22, 2015 #2

    andrevdh

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    Homework Helper

    How did you get at the answer for a?
     
  4. Apr 22, 2015 #3

    collinsmark

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    Gold Member

    It doesn't look right to me. How did you come about those answers?
     
  5. Apr 22, 2015 #4
    Well that is the problem ,,, I just use g instead of a
     
  6. Apr 22, 2015 #5
    Oh right to find a Can I use F=ma
     
  7. Apr 22, 2015 #6
    x= 32 m
    W= 576 J
    KE = still 48 J

    Am I right ??
     
  8. Apr 22, 2015 #7

    collinsmark

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    Gold Member

    The first two look somewhat promising (I'd be more definitive about it though if you showed your work).

    The third one doesn't look so promising.

    How did you come about your answers? (Hint: in the final answer, I think you forgot to square something.)
     
  9. Apr 22, 2015 #8

    gneill

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    Staff: Mentor

    Now that can't be true! How are you doing any calculations?
    What equations of motion and/or energy do you know?
    You need to show how you got your results. We can't just confirm results, we need to see your work. In that way we can help you to understand where your process is correct or incorrect.
     
  10. Apr 22, 2015 #9
    Okey

    (a) F=ma
    18=8a
    a=2.25
    v^2=v0^2+2ax
    x= 32m

    (b) W=Fd
    = 18(32)
    = 576 J

    (c) KE= 1/2 mv^2
    = 8(144)/2
    = 576 J
     
  11. Apr 22, 2015 #10

    gneill

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    Staff: Mentor

    Yes! Well done for each!
     
  12. Apr 22, 2015 #11
    Thank you so much !!!
     
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