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Galgenstrick
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Special relativity Length Contraction and Time dilation question
Planet X is 18 Light Years from earth, A spaceship moving towards the Earth at a speed of 0.82C (Measured from Planet X) fires a series of 1.2 cm long and 2.1 gram mass (as measured by the pilot) projectiles with a speed of 0.72C (Measured by the pilot) towards the earth. At the moment the projectiles were fired the pilot measured his distance from the Earth to be 1.3 light years.
a.) From the point of view of the observer on earth, how far away is the spaceship from Earth when it starts firing?
There are parts b-f, That I will add later if I get stuck on these as well.
L'=L / [tex]\gamma[/tex]
I am having two difficulties. First, the speed of the spaceship is 0.82C as measured by Planet X, is this the velocity I need to answer the question? or do I need to find the velocity as it would be measured by the earth?
Second, Is there "negative velocity" in this equation? What I mean is, since the spaceship is traveling towards the earth, would the velocity be negative? Or is velocity always positive whether or not an object is moving towards or away from you?
Homework Statement
Planet X is 18 Light Years from earth, A spaceship moving towards the Earth at a speed of 0.82C (Measured from Planet X) fires a series of 1.2 cm long and 2.1 gram mass (as measured by the pilot) projectiles with a speed of 0.72C (Measured by the pilot) towards the earth. At the moment the projectiles were fired the pilot measured his distance from the Earth to be 1.3 light years.
a.) From the point of view of the observer on earth, how far away is the spaceship from Earth when it starts firing?
There are parts b-f, That I will add later if I get stuck on these as well.
Homework Equations
L'=L / [tex]\gamma[/tex]
The Attempt at a Solution
I am having two difficulties. First, the speed of the spaceship is 0.82C as measured by Planet X, is this the velocity I need to answer the question? or do I need to find the velocity as it would be measured by the earth?
Second, Is there "negative velocity" in this equation? What I mean is, since the spaceship is traveling towards the earth, would the velocity be negative? Or is velocity always positive whether or not an object is moving towards or away from you?
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