Originally posted by: Giscardo
Originally posted by: GRagland
On a slightly other topic... What does this physics problem mean?
- A spring of constant k is initially compressed a distance Xo from its unstretched length. What is the change in potential energy if it is then compressed to an amount X from its unstretched length?
Im not sure what they mean by Xo, does it mean X=0, in which case the spring would not be compressed initially. If so that would be a werid way to word it ("initially compressed a distance 0 from its unstretched length...") Anyone know?
part B of that problem is:
- Suppose the spring is then stretched a distance Xo from the unstretched length. What is the change in potential energy as compared to when it is compressed by an amount Xo?
WTF!
Xo is just a number, doesn't matter what number. It's not zero, it was compressed from X=0, to a point Xo meters (or whatever units) from X=0.
TO find the change in potential engergy for part A you want to first find the potential energy when it is compressed to Xo, by plugging in Xo for X into the formula E = -kX^2 or whatever it was.
TO solve part B, they are saying that instead of compressing you pull the spring by the same distance. the change in potential energy is the same since the distance is the same? Even though the signs of Xo from partA and partB are different because they are in different directions from the uncompressed point, when you square X in the formula -kX^2, the sign goes away.