What is the Force Exerted by a Spring in a Moving Elevator?

[mrshappy0]

Homework Statement

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?

Homework Equations

f=-kx

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?

 

[edgepflow]

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]

Still not sure how to solve this I guess

 

[flyingpig]

Draw your Free-Body Diagram first.

 

[SammyS]

How is it this possible "... a motionless elevator. the elevator is moving " ?

Follow flyingpig's advice !

 

[PeterO]

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.