Question 18N.3.SL.TZ0.3
| Date | November 2018 | Marks available | [Maximum mark: 4] | Reference code | 18N.3.SL.TZ0.3 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain, Hence, Show that, State | Question number | 3 | Adapted from | N/A |
The diagram shows the axes for two inertial reference frames. Frame S represents the ground and frame S′ is a box that moves to the right relative to S with speed v.
State what is meant by a reference frame.
[1]
a set of rulers and clocks / set of coordinates to record the position and time of events ✔
When the origins of the two frames coincide all clocks show zero. At that instant a beam of light of speed c is emitted from the left wall of the box towards the right wall. The box has proper length L. Consider the event E = light arrives at the right wall of the box.
Using Galilean relativity,
explain why the time coordinate of E in frame S is .
[2]
ALTERNATIVE 1:
the time in frame S′ is ✔
but time is absolute in Galilean relativity so is the same in S ✔
ALTERNATIVE 2:
In frame S, light rays travel at c + v ✔
so ✔
In Alternative 1, they must refer to S'
hence show that the space coordinate of E in frame S is .
[1]
x = x' + vt and x' = L ✔
«substitution to get answer»