# What is Spring Force?

M.J. Casey
M.J. Casey

A spring is an object that upon application of a force in a given direction compresses and then, after removal of the force, decompresses or springs back to its original dimension. Spring force is the description of the force that causes the spring to rebound. It is a characteristic of the material at a molecular level and its three-dimensional shape on a macro level. Hooke’s law is the customary formula for calculating this force.

Constant pressure on a surface may be all that is required of a spring in a mechanism. Springs in a car’s shock absorbing system are not calibrated to measure deflection but to absorb the energy transmitted from the wheels to the car. In many small appliances or electrical devices, switches consist partly of a piece of metal stripping acting as a spring. The strip changes shape as pressure is applied, which then connects a new set of electrical contacts.

In other applications, springs provide a proportional quantitative feedback to the user. When measuring a weight, the spring force is compressed a distance proportional to the pull of gravity on the weight. The more closely a linear response is observed, the better a given material and configuration will suffice in a metrology application. Materials stretched beyond their elastic limit will no longer respond as a spring.

Springs are not considered a type of simple machine, as they do not transfer force through a distance. They need to deflect or stretch through a distance to absorb the energy applied to the spring. Most of the energy is released back in the original incoming direction. The spring force is always applied at the incident angle. Some energy is lost as heat.

Hooke’s law states that force is equal to the negative of the spring constant multiplied by the distance. As long as a spring is functioning within its elastic limits and responds proportionately to the applied force, the spring is a Hookes-law spring and its material is considered so. These materials are said to have a linear-elastic property and will have a characteristic spring constant. The negative sign is the result of the resultant force from the opposite direction of the incident force.

In the new field of microelectromechanical systems (MEMS), also called micro-machines, microscopic springs have been made. These nano-scale springs are made from films etched in a way similar to integrated circuit (IC) packages. Researchers have demonstrated Hookean behavior and have used them as tiny rulers or probes to detect surface variations.

## You might also Like

nony

@hamje32 - Yeah, different types of springs will affect the firmness or softness of a mattress.

The first bed I bought was terrible. It was firm for about one year, and then after that it started to sag. There was no more spring left in it.

I couldn’t believe it went bad so quickly. It was supposed to be a good mattress, but I got it on sale – I guess you get what you pay for. Like you, I finally switched to a better mattress, even though it meant paying a little bit more. But I slept like a baby.

hamje32

@nony - Springs play an important role in a lot of everyday consumer goods, like spring mattresses.

I suffered from back pain for years until I finally got rid of my old bed and got a good quality spring mattress. It took some time to make the right decision, however, because I had certain mistaken notions about what would be the best quality mattress for my back.

For example, I thought a mattress that was super firm would be the ideal bed for my back, but it certainly didn’t feel that way at first. Then I spoke with my doctor and he said that actually medium-firm mattresses were the best; they would help to support my back and provide comfort as well.

So I bought a good quality medium firm mattress and my back pain is nearly gone.

nony

@miriam98 - If it’s any consolation, sometimes springs get worn a little. They lose some of their “springiness,” if you will, and in that case you will need to calibrate your scale.

I went to a digital scale some time ago because it didn’t use springs and so I thought it would give me improved accuracy. It did, but not as much as I thought.

Once I had calibrated the original spring scale, my readings were very close to what I got on the new digital scale.

miriam98

It’s too bad that you can’t cheat the force of a spring in some situations. Last week I got on the scale in the bathroom to check my weight, and the spring kept getting more and more compressed with the full force of my weight.

After it was compressed, I was depressed. The readings on the scale showed that I had regained some of the weight that I had lost in the prior weeks when I had completed my latest fad diet.

Oh well, I guess I’ll have to go back to fruits and vegetables again – and eating nuts like a squirrel.