Let me introduce for your attention a very interesting mechanical system.
It is called: "Varipend." Variable pendulum ( VariPend = VARIable + PENDulum)
A pendulum of variable length and mass, implemented in an isolated system.
- the case increases its mass - working moving mass decreases The mass of the entire system is unchanged!
[math]M(t) = {m_{liquid}}(t) + {m_{case}}(t) = const[/math] The total momentum of the Varipend system:
[math]{{\vec p}_{var}}(t) = {m_{liquid}}(t)\;{{\vec v}_1}(t) + {m_{case}}(t)\;{{\vec v}_2}(t)[/math]
In Mechanics, there is a Law of Conservation of Momentum (LCM):
Which states that the TOTAL MOMENTUM of the mechanical system - without external forces - IS STABLE.
Here is this system, in this form:
The total momentum is LINK DELETED !
This suggests that “external forces” act on this system in this form!
If you release the system from external influences, then the LINK DELETED of this system will look like this:
This is a simple solution to a LINK DELETED!
[math]{p_{var}}(t) = {m_{liquid}}(t){{\vec v}_1}(t) + {m_{case}}(t){{\vec v}_2}(t) = 0[/math]
You can explore the same mechanical system by solving the LINK DELETED
This solution is using a mechanical Lagrangian :
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Before you is the law of conservation of momentum and the law of conservation of energy! In pure form!
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This task is not mathematically complicated.
But she is very, very difficult in terms of psychology ....