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Homework Statement
At what speed does a girl need to travel, if her journey begins in 2009 and she wants to come back two years older in the year 2018.
^^^Can someone please check my answer. I am new to the topic
Homework Equations
T = To / sqrt(1-u^2/c^2)
The Attempt at a Solution
T(earth) = 9 yrs
To(girl) = 2 yrs
9 = 2 / sqrt(1-u^2/c^2)
81 = 4 / 1-u^2/c^2
81(1-u^2/c^2) = 4
(1-u^2/c^2) = 4/81
- u^2/c^2 = 4/81 - 1
u^2/c^2 = 1 - (4/81)
u^2 = 77/81*c^2
u = .974996043 c
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