Are the Forces Different in Parallel and Series Springs?

In summary, in configurations (a) and (b), the equivalent spring constant is k_1+k_2 but in configuration (c), the equivalent spring constant is k_1. In configuration (d), the equivalent spring constant is k_1+2k_2 which is just k.
  • #1
posto002
26
5
Homework Statement
You are given four springs, each with a spring constant k. What arrangements using all
four springs will result in an equivalent spring constant of k?
(a) All four springs in series.
(b) All four springs in parallel.
(c) Three springs in parallel which are then connected in series with the fourth spring.
(d) Two springs in parallel then connected in series with the other two springs which themselves
are in parallel.
(e) No arrangement of the four springs will result in an equivalent spring constant of k
Relevant Equations
Hooke's law
I know that in parallel springs, x (the displacement of the spring) is the same for both springs. However, the forces resulting for each string are different. For springs in a series, x may be different, but the force is the same on each string. I got the answer b, seeing how the weight would be evenly distributed between the four springs. A simple 'yes' or 'no' on whether I answered the question right will suffice. Thank you for any help!
 
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  • #2
posto002 said:
Homework Statement: You are given four springs, each with a spring constant k. What arrangements using all
four springs will result in an equivalent spring constant of k?
(a) All four springs in series.
(b) All four springs in parallel.
(c) Three springs in parallel which are then connected in series with the fourth spring.
(d) Two springs in parallel then connected in series with the other two springs which themselves
are in parallel.
(e) No arrangement of the four springs will result in an equivalent spring constant of k
Homework Equations: Hooke's law

I know that in parallel springs, x (the displacement of the spring) is the same for both springs. However, the forces resulting for each string are different. For springs in a series, x may be different, but the force is the same on each string. I got the answer b, seeing how the weight would be evenly distributed between the four springs. A simple 'yes' or 'no' on whether I answered the question right will suffice. Thank you for any help!
Do the algebra. If one spring is displaced by x, what is the displacement of the others? What net force will result?
 
  • #3
Oh! Right, thank you! That completely went over my head!
 
  • #4
No b) is not the correct answer.

You can find the correct answer if you know that when two springs are connected in parallel, then the equivalent total ##k_{eq}## is ##k_{eq}=k_1+k_2## while if they are connected in series then the equivalent ##k_{eq}## is ##\frac{1}{k_{eq}}=\frac{1}{k_1}+\frac{1}{k_2}##.

Using these basic equations you can calculate the ##K_{eq}## for each of the configurations (a) to (d) and see which turns out to be equal to just ##k##.
 

1. What is the difference between springs in series and parallel?

When springs are connected in series, they are attached end to end, while in parallel, they are attached side by side. This means that when a force is applied to the series arrangement, it is distributed equally between the two springs, whereas in parallel, each spring receives the full force.

2. Which arrangement is stronger?

In terms of strength, the parallel arrangement is stronger because each spring receives the full force, resulting in a greater combined force compared to the series arrangement. However, the stiffness of the individual springs must also be taken into account.

3. How do the forces combine in each arrangement?

In a series arrangement, the forces from each spring add together, resulting in a greater combined force. In a parallel arrangement, the forces are equal, but act in different directions, resulting in a greater combined displacement.

4. Can springs of different stiffness be connected in series or parallel?

Yes, it is possible to connect springs of different stiffness in either series or parallel. However, the overall stiffness of the system will be affected. In a series arrangement, the overall stiffness will be equal to the sum of the individual spring stiffness, while in a parallel arrangement, the overall stiffness will be less than the stiffness of the stiffest spring.

5. How do the displacement and force change in each arrangement?

In a series arrangement, the displacement is the same for both springs, but the force is divided between them. In a parallel arrangement, the displacement is divided between the springs, but the force is the same for both. This means that the displacement will be greater in a series arrangement, while the force will be greater in a parallel arrangement.

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