Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Man In Elevator Problem

  1. Nov 28, 2006 #1
    Force Of Man On Elevator

    1. The problem statement, all variables and given/known data

    An 65- kg man stands in an elevator. What force does he exert on the floor of the elevator under the following conditions? The elevator is stationary.
    Answer:637.65N

    The elevator accelerates upward at 2.3 m/s2.
    Answer:787.15N

    The elevator rises with constant velocity of 3.1 m/s.

    While going up, the elevator accelerates downward at 1.7 m/s2.
    Answer:527.15N

    The elevator goes down with constant velocity of 6.3 m/s.

    2. Relevant equations
    EF=0


    3. The attempt at a solution

    so far i have the ones where i allready have the acceleration but i don'tknow how to do the ones with velocity because i don't have a t(time) i thought maybe i could do the same and multiply 3.1m/s*65kg which is 201.5 and then use the formula EF=0 so EF=0=-201.5-637.65 which equals 839.15 but this was wrong, could you just give me an idea on how to get started and help would be greatly appreciated.
     
    Last edited: Nov 28, 2006
  2. jcsd
  3. Nov 28, 2006 #2
    Do I not have enough work swown?
     
  4. Nov 28, 2006 #3

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    you need only to look at newton's first law to arrive at a solution. What is the acceleration of the elevator and person when they are moving at constant speed?
     
  5. Nov 28, 2006 #4
    how do i get to the acceleration when i don't have anything but weight and velocity?
     
  6. Nov 28, 2006 #5
    i have figured it out thank you for your help.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook