Special relativity

Question 1

Describe a natural phenomenon that cannot be explained by Newtonian physics

Answer 1

Muons created 15km up in the upper atmosphere are expected to decay within 7km according to Newtonian physics, however these muons can be detected at the earths surface

Question 2

Define “Frame of reference”

Answer 2

The abstract coordinate system that defines the location of the observer. for example a stationary frame of reference or a moving frame of reference

Question 3

Define “Intertial frame of reference”

Answer 3

Any frame of reference with respect to which the acceleration of the object of observation remains zero

Question 4

Explain the concept of simultaneity

Answer 4

The relationship between two events that are assumed to happen at the same time in a frame of reference

Question 5

What is the consequence of the speed of light being a constant in a vacuum

Answer 5

Time dilation and length contraction

Question 6

Define “time dilation”

Answer 6

the difference of elapsed time between two events as measured by observers moving relative to each other

Question 7

Define “Proper time interval”

Answer 7

The time interval measured in the frame of reference in which the object is at rest

Question 8

Define “relativistic time interval”

Answer 8

The time interval measured in the frame of reference in which the object is in motion

Question 9

Define “length contraction”

Answer 9

An observer at rest relative to a moving object would observe the moving object to be shorter along the dimension of motion

Question 10

Define “Proper length”

Answer 10

the length measured in the frame of reference in which the object is at rest

Question 11

Define “Relativistic length”

Answer 11

the length measured in the frame of reference in which the object is in motion (Symbol L, unit m)

Question 12

Define “rest mass”

Answer 12

The mass of an object when measured in the same reference frame as the observer

Question 13

Define “relativistic momentum”

Answer 13

the momentum of an object when measured in the frame of reference in which the object is in motion (symbol Pv, unit Ns)

Question 14

Describe time dilation ad give an example of experimental evidence

Answer 14

Time in a moving frame seems to pass more slowly to an observer in a stationary frame of reference. muon experiment is example

Question 15

Describe length contraction and give an example of experimental evidence

Answer 15

Motion affects space in the direction of travel. a moving object will appear shorter or appear to travel a shorter distance, by a stationary observer. Muon experiment.

Question 16

Recall the mass-energy equivalence relationship

Answer 16

E=mc^2

Question 17

Explain why no object can travel the speed of light in a vacuum

Answer 17

the relativistic mass or momentum would be so large it would require an infinite force to accelerate it

Question 18

Explain twin paradox

Answer 18

One twin flies away in a spaceship to return to earth to find their twin older. The twin on Earth remains in a non-accelerating frame of reference compared to the twin in the spaceship who is in an accelerating frame of reference and experiences time dilation

Question 19

Recall the Einstein’s two postulates of special relativity

Answer 19

• The laws of physics are the same in all inertial frames of reference
• The speed of light in a vacuum has the same value c in all inertial frames of reference