How Do You Calculate the Final Vector of a Rock Ejected from a Spaceship?

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Discussion Overview

The discussion revolves around calculating the final vector of a rock ejected from a spaceship traveling in a two-dimensional plane in zero gravity. Participants explore the necessary variables and equations involved in determining the rock's trajectory after being ejected at a right angle to the spaceship's forward vector.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant describes the scenario of ejecting a rock 90 degrees to the right of the forward vector and asks for the equation to find the final vector of the rock, noting the final speed is 100.
  • Another participant emphasizes the need for the speed of the spaceship and the speed of the rock at ejection to derive the exact equation, suggesting that the ejection point can be considered the origin for simplicity.
  • There is a discussion about the difference between speed and velocity, with some participants expressing confusion over the terminology used.
  • One participant mentions that if a photon were ejected instead of a rock, the resulting trajectory would differ, although this is noted to be a separate topic of discussion.
  • A later reply proposes a simple equation for the trajectory based on the velocities of the spaceship and the rock, indicating that the equation is straightforward if the spaceship's motion is considered.
  • Another participant critiques the clarity of a previous post, indicating that it lacked meaningful content in the context of the discussion.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the terminology of speed and velocity, and there is no consensus on the exact equation or approach to calculating the final vector of the rock. Multiple competing views and uncertainties remain regarding the necessary variables and the clarity of the discussion.

Contextual Notes

Some participants note the importance of specifying the speed of the spaceship and the ejection speed of the rock, while others highlight the potential confusion surrounding the terms speed and velocity. The discussion does not resolve these uncertainties or provide a definitive equation.

DeckSmeck
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I fly in a spaceship on a 2d plane (for simplicity sake) in zero G. I eject a rock 90 degrees right to my forward vector. What does the equation look like if I want the final vector of the rock?

I know the final speed of the rock is 100.

What variables need to be known about the ship and rock?
 
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DeckSmeck said:
I fly in a spaceship on a 2d plane (for simplicity sake) in zero G. I eject a rock 90 degrees right to my forward vector. What does the equation look like if I want the final vector of the rock?
It will be the equation for a straight line

What variables need to be known about the ship and rock?
To get the exact equation, you'll need the speed of your ship and the speed with which you eject the rock (and to be fully accurate, the place on the graph where the rock gets ejected, but for simplicity you could just take that as being the origin.

If, on the other hand, you were "ejecting a photon", you would get a completely different result. It would still be a straight line, but it would be just a horizontal line* since the motion of your ship would have no effect on the photon.

* I'm assuming your ship is traveling in the postie Y direction.
 
phinds said:
It will be the equation for a straight line

To get the exact equation, you'll need the speed of your ship and the speed with which you eject the rock (and to be fully accurate, the place on the graph where the rock gets ejected, but for simplicity you could just take that as being the origin.

If, on the other hand, you were "ejecting a photon", you would get a completely different result. It would still be a straight line, but it would be just a horizontal line since the motion of your ship would have no effect on the photon.

Speed or velocity?
 
DeckSmeck said:
Speed or velocity?
speed or velocity WHAT ?
 
phinds said:
If, on the other hand, you were "ejecting a photon", you would get a completely different result. It would still be a straight line, but it would be just a horizontal line* since the motion of your ship would have no effect on the photon.

* I'm assuming your ship is traveling in the postie Y direction.

Not talking about photons. Just a rock. Talking about photons in a different thread. If you want to talk about photons we can talk there.
 
phinds said:
speed or velocity WHAT ?
I understand these terms describe different things.
 
DeckSmeck said:
I understand these terms describe different things.
And what is it that you want to know about as regards this thread. Your post
DeckSmeck said:
Speed or velocity?
was meaningless to me.
 
phinds said:
And what is it that you want to know about as regards this thread. Your post

was meaningless to me.

Ok. Maybe someone else can come up with an equation. I will check tomorrow.
 
DeckSmeck said:
Ok. Maybe someone else can come up with an equation. I will check tomorrow.
The equation is utterly trivial. If the plane is flying in the positive Y direction with velocity v1 and the rock is ejected to the right with velocity v2 as the plane passes the origin, then the equation is y=(v1/v2)x
 
  • #10
DeckSmeck said:
I fly in a spaceship on a 2d plane (for simplicity sake) in zero G. I eject a rock 90 degrees right to my forward vector. What does the equation look like if I want the final vector of the rock?

I know the final speed of the rock is 100.

What variables need to be known about the ship and rock?
I recommend reading this link on vector addition:
https://www.physicsclassroom.com/class/vectors/Lesson-1/Vector-Addition

It looks to me like you also need either the speed of the spaceship or the ejection speed of the rock, since you have specified the final speed of the rock (which seems odd...).

Also:
Speed or velocity?
You will get better responses if you write your questions in complete sentences, containing complete thoughts. I believe I know what this question was referring to, but you should have written it out fully.
 

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