Minkowski diagram, where to put an event

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Homework Help Overview

The discussion revolves around the placement of an event within a Minkowski diagram, specifically in the context of two cars, A and B, where B sends a light signal to A. The problem involves understanding the relationship between the light signal and the motion of car A.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the correctness of the Minkowski diagram and whether the event is inside the light cone. There are questions about the relative velocity between the two cars and the specifics of the problem statement, including the speed of car A.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some have raised questions about the initial conditions and the implications of the light signal's timing. There is a recognition of missing information that could clarify the situation.

Contextual Notes

Participants note that the problem statement is translated from French and may lack clarity. There is a specific focus on whether to draw the light cone or the world line of the light signal, and the calculations regarding the event's position relative to the light cone are being scrutinized.

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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