Relativity, how it affects observation.

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Homework Help Overview

The discussion revolves around the effects of relativity on measurements of length and time as experienced by observers in different frames of reference. The problems presented involve scenarios with spaceships traveling at significant fractions of the speed of light, addressing concepts such as length contraction and time dilation.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply concepts of relativity to specific problems involving length and time measurements from different perspectives. Some participants suggest starting with foundational concepts and relevant equations to guide the analysis.

Discussion Status

Participants have shared initial calculations regarding the problems, indicating some progress in understanding. However, there are indications that further clarification of the underlying concepts may still be needed.

Contextual Notes

The original poster appears to be grappling with the implications of relativity on physical measurements, and there is a focus on comparing observations made by stationary observers versus those made by astronauts in motion. The discussion reflects an exploration of these relativistic effects without reaching a definitive conclusion.

chewtoy929
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I'm having a bit of trouble understanding relativity, and would like some help with the following problems:
1. A spaceship passes a stationary observer at a speed that is 80% the speed of light. At rest, this ship is 65m long. What does the observer say about the length of the spaceship? How does this length compare to that
measured by an astronaut inside the spaceship?

2. A spaceship capable of flying 50% of the speed of light, travels from Earth to Proxima Centauri, the star closest to the Earth other than our own Sun at a distance of 4.3 light years. What does an astronaut inside the spaceship have to say about the length of time it takes to reach Proxima Centauri? How does this time compare to that measured by an observer stationed on Earth?

3. On Earth an astronaut has a mass of 75 kg. If they are in a spaceship that is flying at 75% of the speed of light, then what does a stationary observer have to say about the astronaut's mass? What does the astronaut have to say about their own mass?
 
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Why don't you start out with the concepts behind each problem; what will be the general answer to each. Then, what relevant equations do you think you might need?
 
1= 65m from astronaut, 39 observer
2= 7.447818 astronaut, 8.6 observer
3= 75 kg astronaut, ~113 kg observer
 
Looks good!

It sounded like you were having trouble with some of the concepts, however. Are they clear now?
 

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