Homework Help: Twin Paradox problem

[SOLVED] Twin Paradox problem

Here is a problem about twin paradox that I can't quite figure out. I got part a, but I can't get part b. I think that the 6 years spent doing research is kinda throwing me off. Help!!

The International Space Federation constructs a new spaceship that can travel at a speed of 0.910c. Mary, the astronaut, boards the spaceship to travel to Barnard's star, which is the second nearest star to our solar system after Alpha Centauri and is 5.98 ly away. After reaching Barnard's star, the spaceship travels slowly around the star system for 6 years doing research before returning back to Earth.
(a) How much time does the journey take?
11.44913698 years
(b) How much older is her twin Frank when she returns?
? years

 

Yep, I tried doing that, using the formula T=2L/v, added 6 to that, and got 19.1429, but the answer still wasn't right. Do you think I'm doing something wrong?

 

do you mean gamma= 1/sqrt(1-v^2/c^2)? because part 2 asks for the twin who stayed on earth's age, and my book said that the formula for that time, as measured on earth, is T=2L/v. So i figured just do that +6. I used T=2L/(gamma*v) +6 for part a's answer.

The answer I put for part b was T=2*5.98/.91+6= 19.1429, but the homework program says it's wrong.

 

gotcha! thank you!!