1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Elevator Problem

  1. Jan 5, 2010 #1
    1. The problem statement, all variables and given/known data

    The effect of gravity is approximately 1/6 of what it is on Earth. If one were to build an elevator on the moon, (a) what would be the apparent weight of a 65kg astronaut when the elevator accelerates upward at 5 m/s2? (b) What is the acceleration of the elevator if the apparent weight of the astronaut is 500N?

    2. Relevant equations

    F = ma
    m = mass
    m = 65 kg
    w = weight
    w = mg
    a = acceleration
    a = 5 m/s2
    gM = 1.63 m/s2

    3. The attempt at a solution

    The equation I set up for (a) was: ma - mg = w
    OR (65)(5) - (65)(1.63) = w
    OR 325 - 106 = w
    Finally, w = 219N

    For (b) I had the same exact forumla: ma - mg = w
    OR (65)a - (65)(1.63) = 500
    OR 65a - 105.95 = 500
    OR 65a = 605.95
    Finally, a = 9.32 m/s2

    Just wondering, again, if this is right or not. =)
  2. jcsd
  3. Jan 5, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Ouch, you let the plus and minus sign bite you. The acceleration is always in the direction of the net force. The apparent weight (the normal force) and the true weight must act in opposite directions.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook