Special relativity

Question 1

Einstein’s theory of special relativity only works…

Answer 1

in inertial frames - not accelerating ones

Question 2

Name and explain the first postulate which Einstein’s theory is based on (not c)

Answer 2

Physical laws have the same form in all inertial reference frames:

• any physics experiment done in any inertial frame always gives the same result
• impossible to use results of an experiment to determine if you are in a stationary reference frame or one moving at a constant velocity

Question 3

What is a reference frame

Answer 3

a space used to describe the position of an object i.e. a set of co-ordinates at any given time

Question 4

What are non-inertial reference frames

Answer 4

reference frames that rotate or accelerate (not Earth)

e.g. a car going around a roundabout (centripetal force)

Question 5

What are inertial reference frames

Answer 5

reference frames where Newton’s laws hold - they are non-accelerating i.e. move at constant, including zero, velocity relative to each other e.g. a train moving at constant velocity

Question 6

What is the principle of relativity

Answer 6

all physical laws appear the same to all inertial observers

Question 7

Any object within an inertial frame will only change its velocity if

Answer 7

an actual non-zero net force is applied to it

Question 8

Maxwell’s equation:

Answer 8

c = (mu0 * epsiolon0)^-0.5 ~ 3x10^8 m/s
Constants given in formula booklet
Equation given in formula booklet

Question 9

Is the Earth an inertial or non-inertial reference frame

Answer 9

Can be considered inertial

Question 10

Name and explain the second postulate which Einstein’s theory is based on (c)

Answer 10

The speed of light in free space is invariant:

• always has the same value, unaffected by the movement of the observer/light source or reference frame
• stemmed from the assumption that Maxwell’s equations hold in any inertial reference frame