12.3.3-12.3.5 Time Dilation, Length Contraction, Mass and Energy
How do you measure muon decay?
1. Place one detector at a high altitude and one much further down 2. Measure the count rates at the two positions 3. Measure the distance between the two detectors and the speed of the muons
What was Betozzi's experimental method?
1. Release the electrons in pulses and record the time taken for them to travel between A and B using an oscilloscope 2. Measure the distance between A and B - calculate the speed of electrons 3. Electrons are directed at the aluminium target and collide which transfers their KE to thermal which can be calculated using a temperature sensor (mc∆T=KE)
What is length contraction?
An object moving in the same direction as its length looks shorter to an external observer
What is time dilation?
An observer of the two events that are moving at a constant velocity in relation to the events will measure a longer time interval between the two events
What is the experimental evidence for the increase in mass of an object with speed?
Bertozzi's experiment - his graph of kinetic energy against speed had values very close to Einstein's predictions
What happens when you transfer energy away from an object?
Causes the mass to decrease
What happens when you transfer energy to an object?
Causes the mass to increase
What is the rest mass?
Mass of an object when it is at rest relative to the observer
What is experimental evidence for time dilation?
Muon decay - enter the atmosphere at very high speeds to experience significant time dilation
What is Betozzi's experimental setup?
Particle accelerator which could emit electrons with varying kinetic energies
What is relativistic mass?
The increased mass of an object moving at high speed
What is the proper length of an object?
The length of an object as measured by an observer stationary relative to said object
What happens as the object approaches the speed of light?
The mass and energy approaches to infinity, which is impossible as you cannot have an infinite amount of mass and energy, therefore, no massive object can move at the speed of light
What doesn't change during length contraction?
The width of the object
What is proper time?
Time interval between the events measured by an observer that is stationary in relation to the events
