Blog Contest is Back
I posted this question a little bit ago, but it got little action, perhaps because it was hidden among my babblings about autumn and other things.
Here it is again, Whitey's gift certificate to the first correct and complete answer!
Suppose you hold a spring and let it hang vertically. It will be stretched out due to the weight that is hanging from it (or even just due its own weight). What will happen to it, if you let go - let it fall freely (by free-fall, I mean that gravity is the only force on it - assume no air resistance)? Will the top accelerate up or down? Will the bottom accelerate up or down? What will happen to the amount of stretch - same? more? less? Hmmm.... Free Fallin'!
2 comments:
This... is hard to do without the sound lab springs to test. So what do you do- turn to youtube!!!
What I saw was that if you have a spring just chillin, there is going to be tension because of its own weight. And because that weight is all over- so is the tension... at least I think thats what Newton would say... BUT the top of the spring has all the weight underneath it- so it has more tension, and the bottom, well its got nothing underneath it so tension would be zero.
Sooo when let go of the top- it is going to accelerate downwards toward the bottom of the slinky due to gravity and tension, but because the bottom's tension was zero, it just chills in its state of rest until the top meets it and then they accelerate uniformly to the floor.
TAHDAH!!!!
(ps- remember I already bought a shirt, so when you order I want a medium)
some fun phsyics-y videos (the first one is complete with a physics-y song)
http://www.youtube.com/watch?v=w_rQbo7SORc
http://www.youtube.com/watch?v=iSHJKvZBJvk&feature=related
Kristen: Close enough! When you are in town next week, be sure to get your gift certificate!
One little thing though. There IS tension on the bottom of the spring - UP! The rest of the spring is pulling up on it, and gravity is pulling down. No NET force - that is why it chills at rest momentarily... until the tension is relieved by the top of the spring accelerating toward it.
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