Relativity (1 Viewer)

[untouchablecuz]

i just had my physics trial and theres a Q i'm not sure of:

A spaceship travelling at 0.8c covers a distance of 1 lightyear.

a) How long does this this journey take from the perspective of someone on Earth?

b) How long does it take for someone on the ship?

for a) i got 1.25 years

for b) i got 27 days

any help is appreicated

 

[Dumbledore]

i'm not too good at this topic, but i think question 1 is right
2: t0 is the time of the observer, tv(1.25)*sqrt(1-0.8^2) = t0 = 0.75years

remember when given a speed as a % of c u can sub it in as like sqrt(1-[(0.8c)^2]/[c^2]) and the c's will cancel, easier and less chance of mistake

even if u see it as like 2x10^8, change it to 2/3 * c

 

[JasonNg1025]

I think dumbledore is correct
t0 is the time on the ship, so you do it like him
Another way of thinking about it is the ship thinks the length has contracted, either way you're multiplying by sqrt(1-v^2/c^2)

 

[anom1ly]

hmm, i could be wrong, but i get 0.75years for part b

i let 1.25 years be tv, and solved for to

 

[cybob101]

yeah, i get .75 as well

 

[shady145]

i just had my physics trial and theres a Q i'm not sure of:

A spaceship travelling at 0.8c covers a distance of 1 lightyear.

a) How long does this this journey take from the perspective of someone on Earth?

b) How long does it take for someone on the ship?

for a) i got 1.25 years

for b) i got 27 days

any help is appreicated

i had a very simlar question in mine... it was 4 light years as measured form a guy on earth to a distant planet, 0.8c and what was the time for the guy in the spaceship to get to the planet timed by him

 

[cybob101]

i had a very simlar question in mine... it was 4 light years as measured form a guy on earth to a distant planet, 0.8c and what was the time for the guy in the spaceship to get to the planet timed by him

3 years

 

[untouchablecuz]

i'm not too good at this topic, but i think question 1 is right
2: t0 is the time of the observer, tv(1.25)*sqrt(1-0.8^2) = t0 = 0.75years

remember when given a speed as a % of c u can sub it in as like sqrt(1-[(0.8c)^2]/[c^2]) and the c's will cancel, easier and less chance of mistake

even if u see it as like 2x10^8, change it to 2/3 * c

what i did for b was:

L=Lo * sqrt(1-0.8^2)

where Lo is 1 LY and L is the shorter relativistic length

then i proceeded to use t=d/v, where d=L and v=0.8c

well anyway, thanks for the help everyone

 

[mitchell.j.bell]

In one year, light travels a distance of 1 lightyear, so if something was going 0.8 times the speed of light, it would only travel 0.8 times the distance of one light year in one year, i.e 0.8 lightyears.

SO how is everyone getting 0.75 years for part (b)?

 

[darkchild69]

time dilation dude

 

[untouchablecuz]

just so you guys know

i got my paper back

for a) my answer is correct

b) 0.75 years is correct

 

[mitchell.j.bell]

time dilation dude

Touche. I assumed that everyone was giving answers to (a)