PDA

View Full Version : pencil in elevator


lytien
Sep24-09, 06:31 PM
A pencil is dropped from inside an elevator moving 5m/s upward. Calulate the time it takes to drop from 1m to elevator floor and its velocity.


I approached as a velosy problem. Is this more of a Force problem ? I could calculate the velocity and time it took while the elevator was at a standstill, but got stuck when its in motion. Can someone please guide me in the right direction? THanks!

lanedance
Sep26-09, 11:48 PM
maybe show some working so we can see where you went wrong

note the pencil will initially be moving up at 5m/s the same speed as the elevator & have a think about equivalence of inertial reference frames

Phrak
Sep27-09, 12:39 AM
I could calculate the velocity and time it took while the elevator was at a standstill, but got stuck when its in motion. Can someone please guide me in the right direction? THanks!

The concept you should apply is Galilean relativity; the laws of physics are the same in all inertial frames.