AAMC6 #39: Spring Question (what's the effective K?)

[SaintJude]

Answer at the end

Answer is B

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[MedPR]

Why is the answer B?

Imagine pulling the atom to the right. The spring on the right compresses and the spring on the left stretches. Everything wants to be at equilibrium (not stretched, not compressed). So the spring on the right is trying to restore (to the left) with force K, and the spring on the left is also trying to restore (to the left) with force K. K+K=2K.

 

[chiddler]

F = kx

k = F/x

k is the amount of force to move an object x distance on a spring.

that setup would require twice as much force to move some distance, therefore it is 2K.

 

[SaintJude]

Ok, my problem was that I understood additive effects and all, but I didn't understand that the direction of the force was identical for both strings.

So would the result have also been the same if the model looked like this below?

2 strings attached to only one side of the atom:

 

[MedPR]

Ok, my problem was that I understood additive effects and all, but I didn't understand that the direction of the force was identical for both strings.

So would the result have also been the same if the model looked like this below?

2 strings attached to only one side of the atom?

I think so.

 

[chiddler]

yeah it would be exactly the same. the direction of forces that each spring exerts remains unchanged and it still requires twice as much force to move a given distance.