MODULE 7 IQ 4

Question 1

what is a frame of reference

Answer 1

• a set of coordinate axes and a dimension of time, and we use these sets/dimensions to make observations from our point of view
• if frame of reference is not accelerating, it is known as an inertial frame of reference

Question 2

inertial frames of reference (IFOR)

Answer 2

• not accelerating
• in these frames, newton’s laws of motion hold
• observers in inertial frames can make predictions about motion of objects with relative ease

Question 3

galilean relativity

Answer 3

• describes how the laws of mechanics are the same in all inertial frames of reference
• if you’re in a closed room moving at a constant velocity, you cannot perform any experiment to determine that you’re moving

Question 4

special theory of relativity

Answer 4

• the laws of physics are the same for all observers in inertial frames of reference, regardless of their relative motion
• leads to time dilation, length contraction and the equivalence of mass and energy ( E = mc^2)

Question 5

einstein’s postulates

Answer 5

1. the speed of light in a vacuum remains constant in all inertial frames of reference
2. the laws of physics are invariable in all inertial frames of reference

Question 6

implications of einstein’s 1st postulate

Answer 6

• light is invariant at 1/√ε(0)μ(0) for ALL frames of reference
• relative velocity between the light source and the observe does not alter the measure velocity of light

Question 7

implications of einstein’s 2nd postulate

Answer 7

• experiments conducted within inertial frames will yield consistent results
• it is not possible to determine experimentally whether an inertial frame is stationary or in motion
• time and distance are not absolute quantities

Question 8

proper time

Answer 8

time an event takes to occur, as measured by an observer with the same frame of reference as the event itself

Question 9

proper length

Answer 9

length of an object, measured in a frame of reference that observes the object at rest (not moving)

Question 10

time dilation

Answer 10

• velocity of object increases, the factor by which its time dilates increases
• for outside observer: light needs to travel a longer distance (longer time observed)
• for inside observer: no change in distance (shorter time)

Question 11

time dilation equation

Answer 11

t = t(0)/√1-v^2/c^2
t: dilated time
t(0): proper time

Question 12

length contraction

Answer 12

• length appears shorter for a moving observer
• length appears longer for stationary observer

Question 13

length contraction equation

Answer 13

l = l(0)√1-(v^2/c^2)
l: contracted length while in motion (observer moving with respect to distance’s endpoints)
l(0): proper length (observer at rest in reference to distance’s endpoints

Question 14

simultaneity

Answer 14

• reality is not different for 2 observers in different frames

Question 15

evidence for special relativity

Answer 15

hafele-keating experiment, muons