# Tagged Questions

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### Do we need inertial frames in Lagrangian mechanics?

Do Euler-Lagrange equations hold only for inertial systems? If yes, where is the point in the variational derivation from Hamilton's principle where we made that restriction? My question arose ...
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### How are fictitious forces related to my feeling?

This question arises when I am studying fictitious forces in an undergrad introduction to physics course. Suppose I am standing in an elevator with an acceleration $a$ directed upward. From the ...
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### What is the Earth truly rotating about/revolving around?

Earth rotates on its axis and revolves around the sun, the sun revolves around the galaxy, the galaxy is also moving. So Earth's net rotation as observed from a fixed inertial frame consists of all ...
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### How to create frame of reference?

Is this possible to create a inertial frame of reference in the earth? How it is possible?
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### Foucault pendulum

The equations of motions for a Foucault pendulum are given by: $$\ddot{x} = 2\omega \sin\lambda \dot{y} - \frac{g}{L}x,$$ $$\ddot{y} = -2\omega \sin\lambda \dot{x} - \frac{g}{L}y.$$ What are the ...
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### The form of Lagrangian for a free particle

I've just registred here, and I'm very glad that finally I have found such a place for questions. I have small question about Classical Mechanics, Lagrangian of a free particle. I just read Deriving ...
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### Deriving the Lagrangian for a free particle

I'm a newbie in physics. Sorry, if the following questions are dumb. I began reading "Mechanics" by Landau and Lifshitz recently and hit a few roadblocks right away. Proving that a free particle ...
The other day we derived Kepler's third law. $$\left( \frac{T_1}{T_2} \right)^2 = \left( \frac{r_1}{r_2} \right) ^3$$ In order to derive this, you can look at a given planet that revolves around ...