1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Trying to solve an elevator problem

  1. Feb 6, 2013 #1
    1. The problem statement, all variables and given/known data
    An elevator accelerates downward at 3.2 m/s2. What force does the floor of the elevator exert on a 46 kg passenger?


    2. Relevant equations

    T+F=ma
    T being tension

    3. The attempt at a solution
    I don't know if the tension of the elevator line is 9.81N, and in the passenger I got 147.2 N for his force(using the acceleration of the elevator.
     
  2. jcsd
  3. Feb 6, 2013 #2
    You don't need the tension of the elevator cable here since it doesn't directly act on the passenger.

    Draw a free-body diagram for the passenger and use Newton 2.
     
  4. Feb 6, 2013 #3
    so i basically get the force of the person by, multiplying 49kg*3.2m/s^2 right? if so, then how do I get the force of the floor? it is less because the elevator is going down right?
     
  5. Feb 6, 2013 #4
    What are the 2 forces acting on the passenger?
    Draw these on a diagram and add them.
    Their sum will be the quantity you calculated.
    ( Make sure that your signs are correct here ).

    You are right in saying that the normal force will get less.
     
  6. Feb 6, 2013 #5
    so, the answer would be 137.39N ? because of the substraction of the normal force of the man and the default force 9.81N?
     
  7. Feb 6, 2013 #6
    No.

    The normal force on the passenger acts upwards, and the weight acts downwards.
    The sum of these is the quantity you calculated in #3, ( from F(net) = ma ).

    You can work out the normal force from this.
    Choose one direction as positive ( eg the downward direction ) and make sure your signs are correct.
     
  8. Feb 6, 2013 #7
    so it would be 304.06 - 147.2 = 156.86N
     
  9. Feb 6, 2013 #8
    Where does the 304.06 come from?

    You should have something like
    mg - n = ma
     
  10. Feb 6, 2013 #9
    well, is (9.81-3.2)*46= 304.06 and that's the final answer.
     
  11. Feb 6, 2013 #10
    Yes :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Trying to solve an elevator problem
  1. Elevator problem (Replies: 7)

  2. Elevator Problem (Replies: 5)

Loading...