time dilation what am i doing wrong? (1 Viewer)

[astroman]

a 5000kg spaceship is 25m long and 6m wide when at rest. if the spacecraft is travelling at 0.995c in the direction of the length of the craft from the frame of reference of an observer on earth, calculate:

- the time that elapses on the spacecraft if 1hr passes on earth whilst the craft is travelling at this relativistic speed.

 

[anomalousdecay]

Your t_v and t_o is the other way around.

 

[astroman]

facepalm

 

[anomalousdecay]

facepalm

That gives you the right answer correct?

Also, do you feel a bit confused about which is t_v and t_o sometimes? I usually had confusion about that quite a bit but I can explain it to you (once I read up on it to remember how to explain it properly ) if you like.

 

[astroman]

yea it's correct, if you wanna explain it would be appreciated.

 

[astroman]

if someone can please show how to do this would also be great,

14. The houses in a street draw 4A of current at 240V. The supply current to these houses is
from an 11kV substation. Assuming no energy losses, what would be the current flow
through the substation?
(A) 0.087A
(B) 0.183A
(C) 87.3A
(D) 183A

 

[Kaido]

v(primary)I(primary)=v(secondary)I(secondary)
sub in and yeah
(law of cons. of E)

 

[astroman]

v(primary)I(primary)=v(secondary)I(secondary)
sub in and yeah
(law of cons. of E)

don't get, can u link to a formula plz

 

[Kaido]

As for the explanation, we want to calculate the time on the spaceship (and we are also onboard). The time on earth relative to us is 1 hour. So the relativistic time is 1 hour.
As a guide, relativistic time>rest time, so we should obtain a lower value

(i have no clue what im saying, please dont hate)

 

[Kaido]

don't get, can u link to a formula plz

check ur formula sheet, if not, then textbooks. this is related to transformers

 

[astroman]

cant find on formula sheet plz find

 

[anomalousdecay]

if someone can please show how to do this would also be great,

14. The houses in a street draw 4A of current at 240V. The supply current to these houses is
from an 11kV substation. Assuming no energy losses, what would be the current flow
through the substation?
(A) 0.087A
(B) 0.183A
(C) 87.3A
(D) 183A

I encourage you to post questions like this in the marathon thread from now on

 

[anomalousdecay]

You might find this helpful.

http://newt.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm

I'm still unsure how to explain it myself because I usually just look at it and do the question based on what is what. Time will always seem to tick slower for the spacecraft iff the observer at rest is seeing it (that was a bad and possibly confusing explanation by me oops).

I think the best explanation I can think of is that t_o is the observed time in the observed reference frame (so we take this as the frame that is being defined at rest) and t_v is the observed time in one frame in reference to the other (the one which we say is moving relative to the one we chose to be at rest from the question).

This also is the same for length and mass dilation.

If you ever forget: faster --> shorter in length, slower clock ticks and heavier mass relative to a frame of reference at rest. Then you can apply that to the formula to remember what is what.