Mysterious Slinky with mass

Classical Mechanics Level 2

Slinky is a helical spring-like toy which can be easily extended to great lengths.

Imagine a slinky with mass $M$ tied at the lower end is hung at its upper end and suddenly it is released to fall freely. How will its lower end (including mass) move till the slinky achieves its natural length?

Try the Inspiration first .

The lower end will move upward to meet the upper end somewhere in the middle The lower end will move downwards The lower end will stay at its place

2 solutions

Md Zuhair
Jan 23, 2017

This is not a solution as my question has some mass attached to the lower end of the slinky. you must explain too.

Rishabh Deep Singh - 4 years, 4 months ago

Same applies to that also, As the lower part is at rest it will tend to keep itself at rest when no external force acts, Its Spring force is cancelling with the mg of the block keeping it in rest. Thank you

Md Zuhair - 4 years, 4 months ago

Michael Mendrin
Jan 23, 2017

The mass $M$ is stationary because of the tension of the spring at the bottom where the mass is attached to it is counteracting the gravitational pull on the weight. For $M$ to start moving, the amount of tension in that bottom part of the spring has to change. When the spring is suddenly released at the top, the change in tension in the spring does not occur instantaneously along its entire length, but instead travels from the top to the bottom, and that takes a certain amount of time. Hence $M$ will remain stationary until the "wave" of change in spring tension reaches the bottom from the top.

See Will it move? , which is related to this phenomenon.

Mysterious Slinky with mass

2 solutions

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