Minkowski diagram, where to put an event

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
6 replies · 2K views
Redwaves
Messages
134
Reaction score
7
Homework Statement
At t=0 A is moving
At t = -1/3 ms B is at 300km north and send a light beam
Draw the Minkowski diagram then tell if the light beam will reach A
Relevant Equations
##-\frac{1}{3} ms = -\frac{10^{-3}}{3}s##
##300km = 3\cdot10^5 m##
##ct = -\frac{10^{-3}}{3}s \cdot c##
I drew the Minkowski diagram, but I'm not sure if this is correct.
From what I drew the angle between x and ct ##\approx 0##
then the event is "inside" the light ray and will eventually reach A.
AvEzfoO.png
 
Physics news on Phys.org
Chestermiller said:
Is there any relative velocity between A and B, and if so, how much?
No, that's all I have
 
Chestermiller said:
Well, it seems like there is something missing from the problem statement. What is the exact wording?
The statement is in french, here is the google translate.

A and B are two cars At t = 0, car A starts to move forward. B sent a light signal to try
to warn him: B is 300 km to the North and sends his signal at t = - (1/3) ms;

I have to draw the world line of that light signal
I'm wondering if I should have draw the cone of light instead of the diagram above?

Thus, since opposite/adjacent < 1, the event in inside the cone of light and if the event in inside the cone of light, the light signal will eventually reach A. Is it correct?

Edit: Since ##ct = 300000000 \cdot -\frac{10^{-3}}{3} = 100000m##
And ##100000/300000 < 1## this is not inside the cone of light, so it will not reach A.
 
Last edited:
Redwaves said:
The statement is in french, here is the google translate.

A and B are two cars At t = 0, car A starts to move forward. B sent a light signal to try
to warn him: B is 300 km to the North and sends his signal at t = - (1/3) ms;

I have to draw the world line of that light signal
I'm wondering if I should have draw the cone of light instead of the diagram above?

Thus, since opposite/adjacent < 1, the event in inside the cone of light and if the event in inside the cone of light, the light signal will eventually reach A. Is it correct?

Edit: Since ##ct = 300000000 \cdot -\frac{10^{-3}}{3} = 100000m##
And ##100000/300000 < 1## this is not inside the cone of light, so it will not reach A.
Any information on the speed with which car A starts to move forward?
 
Chestermiller said:
Any information on the speed with which car A starts to move forward?
That's all I have.