Topic 2B - Relativity Flashcards
what is an inertial reference frame?
A frame in which Newton’s law apply
What are the two postulates of Einstein’s special theory of relativity?
- The speed of light is an absolute constant in and vacuum and in all inertial reference frames
- The laws of physics are the same in all inertial reference frames
Lorentz Factor Equation
Lorentz = 1 / (root) [1 - v(squared) / c(squared)]
Time dilation equation (moving reference frame)
t0 = t’/ Lorentz
Length contraction equation (moving reference frame)
L0 = L’ / lorentz
Time dilation equation (stationary reference frame)
t’ = lorentz x t0
Length contraction equation (stationary reference frame)
L’ = L0 x lorentz
What is muon decay?
How is the theory of relatively relevant to this phenomenon?
Cosmic rays interact with atmosphere and form muons. These radioactive particles have a very short half life and decay quickly.
However, these particles are found 14 km below on the surface of the earth which should be impossible due to their short life.
But they travel close to the speed of light. As such, the theory of relativity can be used to explain the presence of muons of the earths surface. The time for the stationary observer dilates so it is larger.
For the muon, length contracts and therefore it is able to reach the ground.
What is time dilation?
Refers to the slowing down of clocks that are in motion relative to an observer
What is length contraction?
Refers to the decrease in length of an object that it is motion relative to an observer
What is the Lorentz factor?
A ratio that indicates the factor by which length time and mass will change in a moving reference frame when compared to the stationary value.
What is Rest Mass?
m0 is defined as the mass of an object when it is at rest relative to an observer.
