# Homework Help: Lorentz Transformations vs Galilean Transformation

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1. Mar 12, 2017

### Kudox117

1. The problem statement, all variables and given/known data

2. The attempt at a solution

3. Relevant equations

In the first problems of that book i was using the Galilean transformations where

V1 = V2 + V

But if i use that then
V1 = 0.945 - 0.6
V1 = 0.345

Is not the same result, so im confused.
In this new problems we are using Lorentz transformations.
When i should use Galilean transformations and when to use Lorentz transformations?

2. Mar 12, 2017

### TJGilb

Lorentz transformations should always yield you the correct answer, but Galilean transformations are typically accurate for speeds much less than the speed of light. One way to think of it is that anytime you are using units in terms of c, you should be working in terms of Lorentz transformations. I'm not aware of an actual official cutoff point, but any typical speeds you're going to find here on earth you can use Newtonian physics, with the exception of perhaps objects in orbit such as our GPS satellites.

3. Mar 13, 2017

### David Lewis

It depends on how sensitive the phenomenom under investigation is to relativistic effects. For example, even though electrons (usually) move slowly through a current carrying wire, a small amount of length contraction causes significant magnetic field to arise.