Amelia and Caspar are twins and are 25 years old when Amelia accepts a commissio

Question

Amelia and Caspar are twins and are 25 years old when Amelia accepts a commission to fly to Tau Citi and back. Tau Citi is a star about 8 light years away. Amelia flies directly to the star and without waiting around, comes directly back to earth. You can take her speed as being a constant, despite the fact that her velocity vector flips sign upon her arrival at the star. Caspar is 50 years old when Amelia arrives back on earth. What is Amelia's average speed in Caspar's reference frame? Give your answer as a fraction of the speed of light. How old is Amelia when she returns to earth?

Explanation / Answer

(A) distance AMelia travels = 8 + 8 = 16 lightyears

time taken = 50 -25 = 25 years

average speed = distance / time = 16 / 25 = 0.64c

(B) for amelia, time will be shorter by the factor of Y.

Y = 1 / sqrt[1 - (v/c)^2]

Y = 1/ sqrt[1 - (0.64)^2] = 1.301

t = 25 / 1.301 = 19.2 years

hence age of Amelia = 25 + 19.2 = 44.2 years old

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.