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Simple Pressure Problem

  1. Nov 27, 2007 #1

    sun

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    1. The problem statement, all variables and given/known data
    A 50kg ballet dancer stands on her toes during a performance with four square inches (26cm^2) in contact with the floor. What is the pressure exerted by the floor over the area of contact? (a) if the dancer is stationary and (b) if the dancer leaps upwards with an acceleration of 4m/s^2?


    2. Relevant equations

    26cm^2=.26m^2
    P=F/A
    F=mg

    3. The attempt at a solution

    For question (a) i got the force to be 50(9.8)=490N, then i divided that by .26m^2. I keep getting an incorrect answer. what am i doing wrong? Also, are there any suggestions on how to set up part (b)?


    I know the answers are: (a) 1.88X10^5Pa, (b)2.65X10^5Pa
    thank you
     
  2. jcsd
  3. Nov 27, 2007 #2

    rock.freak667

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    Homework Helper

    1cm^2=10^-4 m^2
     
  4. Nov 27, 2007 #3

    rl.bhat

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    Homework Helper

    26cm^2=.26m^2. This is wrong.
    26cm^2=26*10^-4m^2.
    In part B force = 50*(9.8 + 4 ) N
     
  5. Nov 27, 2007 #4

    sun

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    Thanks to both of you. What careless errors on my part. :(
     
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