Why L=L(v^2) in inertial reference system?

  • #1
Dr turtle
2
0
TL;DR Summary
Why Landau pointed out that Lagrange function shall only be affected by v square in inertial reference system?
Why he said that beacause space's propertiy is the same in both direction, so L=L(v^2), or do I misunderstand him incorrectly?
btw this conclusion appears in somewhere like page 5 and its about Galilean principle of relativity.
 
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  • #2
The direction should not matter, so only magnitude of velocity |v| should matter.
[tex]f(|v|)=f(\sqrt{v^2})=g(v^2)[/tex]
So we can say only v^2 matters.
 
  • #3
That's really helpful, lots of thanks
 

1. Why does L=L(v^2) in an inertial reference system?

In an inertial reference system, the kinetic energy of an object is given by the formula L=1/2mv^2, where m is the mass of the object and v is its velocity. This equation arises from the work-energy theorem, which states that the work done on an object is equal to the change in its kinetic energy. Therefore, in an inertial reference system, the kinetic energy is directly proportional to the square of the velocity.

2. How is the equation L=L(v^2) derived in an inertial reference system?

The equation L=L(v^2) can be derived by considering the work done on an object to change its velocity from 0 to v. By integrating the force over the distance traveled, we can calculate the work done, which is equal to the change in kinetic energy. This derivation leads to the equation L=1/2mv^2 in an inertial reference system.

3. Does the equation L=L(v^2) hold true in all inertial reference systems?

Yes, the equation L=L(v^2) holds true in all inertial reference systems. This is because kinetic energy is a scalar quantity that depends only on the magnitude of velocity, not its direction. Therefore, the relationship between kinetic energy and velocity remains the same in all inertial reference frames.

4. What are the implications of L=L(v^2) in an inertial reference system?

The equation L=L(v^2) has important implications for understanding the behavior of objects in motion. It allows us to calculate the kinetic energy of an object based on its velocity, which is crucial for analyzing the dynamics of systems and predicting their behavior. This equation forms the basis for many important principles in physics, such as the conservation of energy.

5. Can the equation L=L(v^2) be applied to relativistic systems?

No, the equation L=L(v^2) is a classical formula that applies to objects moving at non-relativistic speeds. In relativistic systems, where velocities approach the speed of light, the equation for kinetic energy becomes more complex and involves the relativistic mass-energy equivalence principle. Therefore, the classical formula L=1/2mv^2 is not valid for objects moving at relativistic speeds.

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