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Oscillating Springs

Hi, I am having trouble understanding oscillating springs. In my textbook it says that as a vertically oscillating spring moves down it gains eleastic potential energy. It then says the elastic potential energy decreases from the lowest to the highest point. It is this bit that confuses me. I thought the elastic potential energy was proportional to the displacement from equilibrium so it should be maximum at either side. If you look at the equation for an oscillating spring it is independent of gravity so how would the spring oscillate vertically in zero gravity if the elastic potential energy is minimum at the top?
Original post by Bibloski
Hi, I am having trouble understanding oscillating springs. In my textbook it says that as a vertically oscillating spring moves down it gains eleastic potential energy. It then says the elastic potential energy decreases from the lowest to the highest point. It is this bit that confuses me. I thought the elastic potential energy was proportional to the displacement from equilibrium so it should be maximum at either side. If you look at the equation for an oscillating spring it is independent of gravity so how would the spring oscillate vertically in zero gravity if the elastic potential energy is minimum at the top?


What you say sounds right, but it's difficult to analyse what the book says without the actual text. We only have here what you say the book says.
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Bibloski
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Original post by Stonebridge
What you say sounds right, but it's difficult to analyse what the book says without the actual text. We only have here what you say the book says.


Well its basically saying that the elastic potential energy decreases as you go from the lowest to highest point of the vertical oscillation. But the equation for the period of an oscillating spring is independent of g. So I guess my question is, how would a vertically oscillating spring work in zero gravity? When it reaches the highest point in its oscillation what brings it back down? Because something must do since it is independent of gravity?
Original post by Bibloski
Well its basically saying that the elastic potential energy decreases as you go from the lowest to highest point of the vertical oscillation. But the equation for the period of an oscillating spring is independent of g. So I guess my question is, how would a vertically oscillating spring work in zero gravity? When it reaches the highest point in its oscillation what brings it back down? Because something must do since it is independent of gravity?


Such a spring can be compressed as well as extended. In all such questions this is an assumption. If not then it's gravity that has to do it. What sort of spring is your book describing? You see, it's impossible to answer your question regarding what the book is actually saying without seeing what the book actually says. You are only telling me a small part of the whole.
Is it a coiled spring that can be compressed? Then you don't need gravity to make it oscillate. A mass on the end would oscillate if the system was placed on a frictionless horizontal table, with the other end fixed. Elastic potential energy is a minimum at the equilibrium position. This is also where kinetic energy is a maximum. The total energy remains constant. If the spring is vertical the you have gravitational p.e. to add in there as well.
Reply 4
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Bibloski
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Original post by Stonebridge
Such a spring can be compressed as well as extended. In all such questions this is an assumption. If not then it's gravity that has to do it. What sort of spring is your book describing? You see, it's impossible to answer your question regarding what the book is actually saying without seeing what the book actually says. You are only telling me a small part of the whole.
Is it a coiled spring that can be compressed? Then you don't need gravity to make it oscillate. A mass on the end would oscillate if the system was placed on a frictionless horizontal table, with the other end fixed. Elastic potential energy is a minimum at the equilibrium position. This is also where kinetic energy is a maximum. The total energy remains constant. If the spring is vertical the you have gravitational p.e. to add in there as well.


Ah I see thanks! I didn't realize springs could be coiled or not. I think this is what confused me as the springs we use in school just snap back and stop so I couldn't see how they could ever oscillate horizontally (even with a friction-less surface). The book doesn't specify that so I would assume it wasn't coiled and then that makes sense from what you said. So if a spring is coiled and you oscillated it vertically in zero gravity would the elastic potential energy be maximum at both the highest AND lowest points then?
Original post by Bibloski
Ah I see thanks! I didn't realize springs could be coiled or not. I think this is what confused me as the springs we use in school just snap back and stop so I couldn't see how they could ever oscillate horizontally (even with a friction-less surface). The book doesn't specify that so I would assume it wasn't coiled and then that makes sense from what you said. So if a spring is coiled and you oscillated it vertically in zero gravity would the elastic potential energy be maximum at both the highest AND lowest points then?


Well, in zero gravity there is no low and high, but I know what you mean. :wink:
For a coiled spring in zero gravity (or in a horizontal position on a frictionless surface, for example) the elastic potential energy is maximum when the spring is extended or compressed the maximum amount. This is because you have to do work against the spring force to extend or compress it. Doing work in this way gives potential energy to the spring.
The springs in school labs that are "closed" and don't compress rely on gravity in a vertical position, of course, to return the mass to equilibrium from the highest point.
(edited 9 years ago)

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