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Problem in solving question related to acceleration and velocity

  1. Jun 7, 2012 #1
    1. The problem statement, all variables and given/known data
    s lift whose cage in 3 m high is moving up with an acceleration of 2m/s^2. A piece of stone in dropped for the top of the cage of the lift when its velocity is 8 m/s, if g = 10 m/s^2, then the stone will reach the floor of the lift after how many seconds?


    2. Relevant equations

    a = (v - u) / t
    d = avg v * t


    3. The attempt at a solution
    I tried to think that if the lift is moving upwards, then when the stone will be dropped it won't have to fall full 3 m because the lift is also moving up so i think we have to add the velocity 8m/s and the velocity with which the stone is moving.
     
    Last edited: Jun 7, 2012
  2. jcsd
  3. Jun 7, 2012 #2
    My interpretation.
    http://img515.imageshack.us/img515/3747/p1010019qd.jpg [Broken]
     
    Last edited by a moderator: May 6, 2017
  4. Jun 7, 2012 #3
    You were right to think that the stone won't have to fall the full 3 meters, since the lift is accelerating upwards. But I'm not sure if that is the easiest way to think about it. Ask yourself: what is the cage/stone system's relative velocity and acceleration?
     
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