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Spring in moving elevator!

by mrshappy0
Tags: elevator, moving, spring
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mrshappy0
#1
Sep26-11, 09:03 PM
P: 98
1. The problem statement, all variables and given/known data

Three masses m1 = 3.1 kg, m2 = 9.3 kg and m3 = 6.2 kg hang from three identical springs in a motionless elevator. the elevator is moving downward with a velocity of v = -2.3 m/s but accelerating upward with an acceleration of a = 4.8 m/s2. (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.) What is the force the bottom spring exerts on the bottom mass?

2. Relevant equations

f=-kx

3. The attempt at a solution

Some of my confusion lies with k. Since k is a constant is it the same value as if the elevator was motionless or does k change when the elevator moves?
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edgepflow
#2
Sep26-11, 11:59 PM
P: 688
Quote Quote by mrshappy0 View Post

Some of my confusion lies with k. Since k is a constant is it the same value as if the elevator was motionless or does k change when the elevator moves?
The spring constant k is constant in the elastic region of the spring. Assume this for your solution.
mrshappy0
#3
Sep27-11, 07:12 PM
P: 98
Still not sure how to solve this I guess

flyingpig
#4
Sep27-11, 07:33 PM
P: 2,568
Spring in moving elevator!

Draw your Free-Body Diagram first.
SammyS
#5
Sep27-11, 08:31 PM
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P: 7,808
How is it this possible "... a motionless elevator. the elevator is moving " ?

Follow flyingpig's advice !!!
PeterO
#6
Sep27-11, 08:36 PM
HW Helper
P: 2,318
Quote Quote by SammyS View Post
How is it this possible "... a motionless elevator. the elevator is moving " ?

Follow flyingpig's advice !!!
I think he means the masses are motionless wrt the lift and not bouncing around - but yes free body diagram.


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