Question 19M.3.SL.TZ2.4
| Date | May 2019 | Marks available | [Maximum mark: 4] | Reference code | 19M.3.SL.TZ2.4 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Calculate, Define, Describe | Question number | 4 | Adapted from | N/A |
The speed of a spaceship is measured to be 0.50c by an observer at rest in the Earth’s reference frame.
Define an inertial reference frame.
[1]
a coordinate system which is not accelerating/has constant velocity/Newtons 1st law applies ✔
OWTTE
Both “inertial” and “reference frame” need to be defined
In defining an inertial frame of reference far too many candidates started with the words ‘ a frame of reference that...... ’ instead of ‘a coordinate system that.....’
As the spaceship passes the Earth it emits a flash of light that travels in the same direction as the spaceship with speed c as measured by an observer on the spaceship. Calculate, according to the Galilean transformation, the speed of the light in the Earth’s reference frame.
[1]
1.5c ✔
Almost no incorrect answers were seen.
Use your answer to (a)(ii) to describe the paradigm shift that Einstein’s theory of special relativity produced.
[2]
c is the same in all frames
OR
c is maximum velocity possible ✔
velocity addition frame dependent ✔
length/time/mass/fields relative measurements ✔
Newtonian/Galilean mechanics valid only at low speed ✔
Most candidates correctly stated that in special relativity the velocity of light, c, is the maximum possible velocity or is invariant. Only a few added that Galilean relativity only applies at speeds much less than the speed of light.
