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Homework Help: F=ma question

  1. Mar 2, 2010 #1
    1. The problem statement, all variables and given/known data
    A person weighing 0.6 kN rides in an elevator
    that has a downward acceleration of 3 m/s2.
    The acceleration of gravity is 9.8 m/s2 .
    What is the magnitude of the force of the
    elevator floor on the person?
    Answer in units of kN.


    2. Relevant equations
    F = ma


    3. The attempt at a solution
    Is the downward acceleration of the elevator and gravity in the same direction, so should the acceleration in the formula equal the sum of the acceleration of the elevator and gravity.
    Or are they in opposite directions?
     
  2. jcsd
  3. Mar 2, 2010 #2

    ideasrule

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    What do you think? Do you feel lighter on an elevator accelerating downwards, or heavier?
     
  4. Mar 2, 2010 #3
    lighter, so would is acceleration due to gravity upwards?
     
  5. Mar 2, 2010 #4

    ideasrule

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    Acceleration due to gravity is downwards because gravity doesn't change; it depends only on the Earth. However, the effect of the elevator's acceleration counteracts the effect of gravity.
     
  6. Mar 2, 2010 #5
    thanks
     
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