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Nov13-12, 06:43 PM
berkeman's Avatar
P: 40,932
Does standing on bathroom scale depress or compress spring

Quote Quote by Conde View Post
Thanks for your reply. I am still confused as to whether when you stand on a scale you are pushing the spring down, which sounds more likely or whether as is written in some books, the spring is pushing up. Also is your weight measured from the scale pushing up, or from your weight pushing down. I appreciate the clarification so I can really understand how the scale works.
In the linear region of the spring's action, the following equation holds:

F = -kΔx

That means that the force F down on the spring will cause its size to shrink in proportion to the force (and in relation to the "spring constant" k). So if object 2 is twice as heavy as object 1, object 2 will cause twice as big of a Δx shrinkage. The movement down of the scale platform is used to turn the indicator to the corresponding weight of the object. The farther down the spring is compressed, the more the dial moves to show the heavier weight.

More info on springs: