HSC 2003 Physics Paper - Question 5 (1 Viewer)

[tpc13]

I'm lost with this. I thought I understood the whole time dilation thing but this keeps throwing me off:

"An astronaut set out on a spaceship from Earth orbit to travel to a distant star in our galaxy. The spaceship travelled at a speed of 0.8c. When the spaceship reached the star the onboard clock showed the astronaut that the journey took 10 years.

An indeitical clock remained on Earth. How much time would the Earth clock say had elapsed?"

Now, I keep getting an answer of 16.7 years, but the BOS answer says that it shows 6 years.

You can work it out for yourself, because trying to get a mathematical formula written in this box is too fiddly right now, but even so, by the principal of the concept, more time should pass on Earth than for astronaut, and the only answer in the multiple choice longer than 10 years is 16.7 Even Wikipedia agrees with me:

http://en.wikipedia.org/wiki/Twin_paradox

According to it, the twin who had travelled was younger than the one on Earth, meaning less time had passed for him, and more time had passed on Earth.

Am I going crazy??? Or is the Board of Studies actually wrong?

EDIT-Spelling

 

[jake2.0]

it has to be (D)

 

[exa_boi87]

I think the question specified the astronauts ship was the frame of reference in which he observed the clock that remained of earth. Remebering the twins paradox showed that both the observer on earth and astronaut both believe that the other person has had less time passed during their journey.

I know what you mean though ... this question got me every time up until last week when i forced myself to wrap my head around the whole frame of reference idea

 

[jake2.0]

oh so its like saying that the earth was moving away at .8c from the space craft

 

[Abtari]

moving clocks run slow

time on earth actually passes quicker than time on spaceship because spaceship is not an inertial frame of reference...hence it's not relli a paradox - i.e. yes, clock runs slower on the spaceship than on earth.

since this is the case, on earth it would seem that more than 10 years has passed

 

[helper]

I would really not worry about this question, as it was a total stuff up on the part of BOS

http://community.boredofstudies.org/showthread.php?t=47456

 

[tpc13]

I would really not worry about this question, as it was a total stuff up on the part of BOS

http://community.boredofstudies.org/showthread.php?t=47456

So we're not going have to deal with this sort of thing? Good.

 

[serge]

So we're not going have to deal with this sort of thing? Good.

you'll have to deal with time dilation etc.
but not BOS making mistakes

 

[tpc13]

Fair enough, though I think I've got the hang of it now. Special relativity doesn't apply to spaceships according to the BOS, but regardless, I can handle the calculations.