Minkowski diagram, where to put an event

AI Thread Summary
The discussion revolves around the correct placement of an event on a Minkowski diagram involving two cars, A and B. Car B sends a light signal to car A, which is 300 km away, at a specific time before A starts moving. Initially, the user believed the event was inside the light cone, indicating the signal would reach A, but later calculations showed it is not within the cone, meaning the signal will not reach A. There is also a request for information about the speed of car A, which remains unanswered. The key takeaway is the importance of accurately determining the position of events in relation to the light cone in Minkowski diagrams.
Redwaves
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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.
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Is there any relative velocity between A and B, and if so, how much?
 
Chestermiller said:
Is there any relative velocity between A and B, and if so, how much?
No, that's all I have
 
Redwaves said:
No, that's all I have
Well, it seems like there is something missing from the problem statement. What is the exact wording?
 
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.
 

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