Special Relativity

Question 1

Describe special relativity

Answer 1

a theory that all motion must be defined relative to a frame of reference; it consists of two principal postulates. It explains how space and time are linked for objects moving at constant speed in a straight line, and forms part of the basics of modern physics.

Question 2

Define Frame of reference

Answer 2

an arbitrary set of axes with reference to which the position or motion of something is described or physical laws are formulated

Question 3

Define inertial frame of reference

Answer 3

a non-accelerating frame of reference in which Newton’s Law of motion are applied

Question 4

recall the 2 postulates of special relativity

Answer 4

1. laws of physics are the same in all inertial frames of reference
2. speed of light in a vacuum has the same value in all inertial frames of reference

Question 5

define simultaneity

Answer 5

the relation between two events assumed to be happening at the same time in a frame of reference

Question 6

explain the concept of simultaneity

Answer 6

two events are simultaneous in a given reference frame if light signals from the events reach an observer who is midway between them at the same time

Question 7

define time dilation

Answer 7

the difference in the time interval between two events as measured by observers moving with respect to each other

Question 8

define proper time interval

Answer 8

the time between the two events measured by an observer at rest to the events

Question 9

define Length contraction

Answer 9

the shorter measurement made by an observer moving relative to the object in the direction of the length being measured

Question 10

define proper length

Answer 10

the length measured by an observer at rest relative to the object

Question 11

define relativistic length

Answer 11

the length as measured by an observer moving with the respect to the object in the direction of motion

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 as measured by an observer moving relative to the object

Question 14

recall the mass-energy equivalence relationship

Answer 14

relates change in mass to the change in energy
E=mc2

Question 15

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

Answer 15

to accelerate an object to the speed of light would require an infinite amount of energy. So, only massless particles such as photons can travel that fast