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: 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?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook