Physics time dilation question, need help! (1 Viewer)

[jimziieboy]

A space ship is sent to Alpha Proxima a distance of 4.2 light years from earth. The space ship travels at a speed of 0.6 c

A) How long does it take to reach Alpha Proxima from the astronauts point of view?
B) From the astronauts point of view how far have they traveled when they arrive at Alpha Proxima?

I'm quite confused with which is To and Tv

 

[jamesischool]

To is from the point of view of the astronauts as they are stationary in relation to the space ship
Tv would be from an observer outside the space ship as they are moving relative to the ship

 

[jimziieboy]

To is from the point of view of the astronauts as they are stationary in relation to the space ship
Tv would be from an observer outside the space ship as they are moving relative to the ship

Ok so would you find what Lv is, so lv = 4.2 sqaure root 1 - 0.6^2 = ___
then you would use the fomurla to = lv / v to find the astronauts view?

 

[jamesischool]

you know what Lv is (4.2 light years) as that's what a stationary observer not under the effects of length contraction observes. so you need to find Lo (point of view of astronaut)
so 4.2 = Lo * square root 1-.6^2
rearrange that to get Lo by itself and you'll get the answer.

 

[jimziieboy]

But aren't we pretty much answering part B first then?
Part b is asking for the astronauts view of how far they travelled.

 

[jamesischool]

right first question is asking for time lol. so you need to figure out the time it would take from a stationary observer (astronaut) view to get there.
Tv = 4.2/6 = 7
v = .6
To = ?
so you get To = 5.6

2nd part
you know Lo = 4.2 and v = .6
so Lv = 3.36

question confused me a ton :/ but the point is that length contracts when you get closer to speed of light (your answer for the astronaut has to be less than 4.2) and time dilates for the relativistic observer (so astronaut's time is shorter)
dont kill me if i got this wrong its been a while :/

 

[jimziieboy]

yeh that makes more sense, Because what I did for question 1 was I found Lv and therefore I used To= Lv/v and will get 5.6 years as so. how ever I'm pretty much answering question b as well, so it wouldn't be a proper working out. So yeh yours makes more sense. ty

 

[jimziieboy]

I really hate these types of questions for physics, so confusing =-='

 

[jamesischool]

question a is just stupid because you have to figure out the time taken first - yea these questions are a pain but they're either done with Lo or Lv as the subject and you can figure out which one you need based on the question so its easy to get them right. you'll probably get one in the HSC as well so easy marks

 

[jimziieboy]

yeh haha, I have my physics half yearly test tommorrow XD