Time dialation

1. May 23, 2010

pmor@hotmail.

An astronaut is travelling at a constant speed of 2.40x10^8 m/s relative to earth through space. according to timing devices aboard the space vehicle the trip took 1.25 years. how long did the trip last if measured relative to earth

2. May 23, 2010

hemantc007

I guess the answer is 2.08333 years.
1.25=x{1-(v/c)^2}^.5
x=2.08333

Last edited: May 23, 2010
3. May 23, 2010

pmor@hotmail.

thats right!!
but how did you get that?
do you need to convert the velocity?

4. May 23, 2010

hemantc007

no you don't because , when we apply the formula (v/c)^2 both v and c are in same units i.e m/s...............

Last edited: May 23, 2010
5. May 23, 2010

pmor@hotmail.

hmm im still not getting the right answer when i plug it in to my calculater..

6. May 23, 2010

DaveC426913

Set the calculator aside, write it out on paper first.

7. May 23, 2010

hemantc007

see the formula is t1 = t2 * { 1 - (v/c)^2 }^(1/2)
where t1 is time in space shuttle (at 2.4...velocity)
t2 is time measured on earth
c is velocity of light
v is velocity of space ship
The above formula is time dilation formula .......
now try it again

ya you could do it on paper too, its easy calculation.........

Last edited: May 23, 2010
8. May 23, 2010

pmor@hotmail.

okay so it would be something like
1.25/ (1-(2.4x10^8)2)^(.5)
which gives me a negative square root

9. May 23, 2010

yuiop

The equation should be x= 1.25/{1-(v/c)^2}^(1/2) with (v/c) and not (c/v).

Use v= 2.40x10^8 m/s and c= 2.99792458x10^8 m/s and you should get the right answer.

10. May 23, 2010

hemantc007

dude it is not v^2 .....but......it is v^2/c^2.........
where c=299792458 m/s and
v is 2.4*10^8 m/s

Last edited: May 23, 2010
11. May 23, 2010

pmor@hotmail.

okay i got ittt finally
thanks guyyys

12. May 24, 2010

DaveC426913

The lesson here, I hope you see, is that, if you rush through the work just to get an answer, you're not paying attention. Setting aside the calculator forces you to ensure that the process leading up to the number at the end is the important part.

13. May 24, 2010

hemantc007

pmor@hotmail.
I am sorry for that mistake i.e replacing c by v...........