On Landau vol.1 Pg.5 (Question about conclusion drawn by Landau)

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SUMMARY

The discussion centers on the derivation of the conclusion that velocity (v) is constant when the Lagrangian (L) is dependent solely on v. The participants clarify that if the derivative of L with respect to v is a function of v, then the time derivative of that function must equal zero, leading to the conclusion that the rate of change of velocity with respect to time (dv/dt) is zero. This establishes that v remains constant under the given conditions.

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zhuang382
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Homework Statement
How do we deduce the conclusion of (3,2)? This is a topic inertial frame.
Relevant Equations
Law of inertia
I understand that d/dv(L) = constant, and L is only dependent on v, but how do we get to the fact that v = constant?
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\frac{\partial L}{\partial v}=f(v),

\frac{d}{dt}f(v)= \frac{df(v)}{dv}\frac{dv}{dt}=0

Usually ##\frac{df(v)}{dv} \neq 0## so

\frac{dv}{dt}=0
 
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