Spring in moving elevator!


by mrshappy0
Tags: elevator, moving, spring
mrshappy0
mrshappy0 is offline
#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
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#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
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#3
Sep27-11, 07:12 PM
P: 98
Still not sure how to solve this I guess

flyingpig
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#4
Sep27-11, 07:33 PM
P: 2,568

Spring in moving elevator!


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

Follow flyingpig's advice !!!
PeterO
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#6
Sep27-11, 08:36 PM
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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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