Why does the bottom part of a slinky stay still when we release the top part to fall?
- Thread starter vokazu
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anarosevoli
Semi-Pro
If you let it drop it will fall according to cumulative mass from bottom to top. And at the very bottom mass is 0, no gravitational force!
It's not much different than taking it up from the ground: It elongates until force needed for further elongation is > than gravitational force (at any point of the slinky!), only after this it completely leaves the ground. On its top it is more elongated than at its bottom because at every point its elongation is relative to the cumulative mass from the bottom up to this point.
It's not much different than taking it up from the ground: It elongates until force needed for further elongation is > than gravitational force (at any point of the slinky!), only after this it completely leaves the ground. On its top it is more elongated than at its bottom because at every point its elongation is relative to the cumulative mass from the bottom up to this point.
But if we replace the slinky with a long vertical golf stick, the bottom of the stick will not stay still right after we drop the stick... The bottom of the stick will fall as soon as we release our hand from the top of the stick.
It must be something to do with the kinetic spring force or something?
Sentinel
Bionic Poster
That's not a good analogy. Maybe try with a ball with a thread or string attached to it.
Hold the ball up with string dangling.
Now drop the ball and see if the string hits the floor first, or the ball catches up with it.
You must drop it from a height.
But the ball is too heavy compared to the string. Maybe just drop a sewing thread without a ball?
I think the spring force pulls the bottom part of the slinky upward but the spring force is fought by the gravitational force, so the bottom slinky stays still for a while as it's being pulled upward and downward at the same time.
I mean, when the guy holds the top part, the slinky is being stretched longer (by gravitational pull), so it potentially will compress or spring back to its original shorter shape after it's released.
If we lay the slinky horizontally on the floor and we stretched it horizontally and then release it, it will compress itself to its original shorter shape. This happens when we stretch it vertically using gravity force while holding the top part with our hand. When we release the top, the slinky will spring back to its shorter form, and the bottom part is being pulled upward by the spring force and downward by gravitational force so it stays still. The top part is pulled downward by both spring force and gravitational force so the only way for the top part is down because nothing is pulling it up.
I mean, when the guy holds the top part, the slinky is being stretched longer (by gravitational pull), so it potentially will compress or spring back to its original shorter shape after it's released.
If we lay the slinky horizontally on the floor and we stretched it horizontally and then release it, it will compress itself to its original shorter shape. This happens when we stretch it vertically using gravity force while holding the top part with our hand. When we release the top, the slinky will spring back to its shorter form, and the bottom part is being pulled upward by the spring force and downward by gravitational force so it stays still. The top part is pulled downward by both spring force and gravitational force so the only way for the top part is down because nothing is pulling it up.
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You should get a Nobel physics prize for this discovery.
Lol, I was good at Physics and Maths at my highschool, but not so good at Chemistry and Biology.
Ok, ChatGPT explains:
When you release the top part of a slinky, gravity pulls it downward. However, the bottom part of the slinky resists moving initially due to inertia. Once the top part reaches the bottom, the force is transmitted through the slinky, causing the bottom part to move. This creates the classic "slinky drop" effect, where the bottom seems to stay still momentarily before the motion propagates through the entire slinky.
When you release the top part of a slinky, gravity pulls it downward. However, the bottom part of the slinky resists moving initially due to inertia. Once the top part reaches the bottom, the force is transmitted through the slinky, causing the bottom part to move. This creates the classic "slinky drop" effect, where the bottom seems to stay still momentarily before the motion propagates through the entire slinky.
Sentinel
Bionic Poster
So ChatGPT should win a Nobel Physics Prize ?
SystemicAnomaly
Bionic Poster
Inertia? Not a satisfying answer to my mind. I liked your explanation in post #7 better. Sounds similar to what our resident tennis physicist, Rod Cross, had to say about this phenomenon.
With the following explanation, the inertia idea make a little bit more sense:
A little bit more insight here:
SystemicAnomaly
Bionic Poster
According to the 3rd video in my previous post, there is a slight delay in the bottom of your stick moving wrt the top end of the stick. A very slight, imperceptible, delay. This would suggest that the stick experiences a slight compression if the top end moves before the bottom end does.
SystemicAnomaly
Bionic Poster
All you need to know is that gravity is a lie… in truth, the Earth sucks.
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