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Questions about Work

  1. May 1, 2014 #1
    1. The problem statement, all variables and given/known data
    Here are two questions I have some trouble answering :
    1- How much work do you do when you hold a bag of groceries while standing STILL?
    2- How much work do you do when carrying the same bag on a distance d across the parking lot of the grocery store?

    2. Relevant equations

    We know that ΔK = W

    3. The attempt at a solution
    1- In the first question , the person stand still so V = 0 and thus ΔK=0 so the work W=0
    2- In the second question, when carrying the bag we only have a gravitational work so W= Wg=0

    IS IT CORRECT ?
     
  2. jcsd
  3. May 1, 2014 #2

    adjacent

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    Gold Member

    First question:
    Yes you are right.There's another way to solve that.
    ##W=F.s## You are applying an equal and opposite force to that of gravity but it's not moving so ##W=F.0=0##

    Second question:
    I don't understand that W=Wg part.
    The question asked how much work you do.
    Use ##W=F.s## and answer!
     
  4. May 1, 2014 #3
    what is F and s ??
     
  5. May 1, 2014 #4

    adjacent

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    Gold Member

    "F" is the force and "s" is the distance in the direction of the force.
    W is the work done.
     
  6. May 1, 2014 #5
    Ah ok , I got it ! Thank you SO MUCH !
     
  7. May 2, 2014 #6

    NascentOxygen

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    Staff: Mentor

    So .... what is your answer http://physicsforums.bernhardtmediall.netdna-cdn.com/images/icons/icon5.gif [Broken]
     
    Last edited by a moderator: May 6, 2017
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