Answer :
Answer:
she'll be 42.3 years old
Explanation:
The year she left is 2020
she returns in 2040
the time observed to have passed by on earth is 40 years
she traveled at a speed of 2.5 x 10^8 m/s
From relativity, the astronaut will experience a time dilation and will age more slowly.
the time that is observed to pass on her ship will be gotten from
t' = [tex]t\sqrt{1 - \frac{v^{2} }{c^{2} } } }[/tex]
where t is the time that is observed to pass by an earthly observer
v is the speed of her ship
c is the speed of light = 3 x 10^8 m/s
v/c = 2.5/3 = 0.83
t' = [tex]40{\sqrt{1 - 0.83^{2} } }[/tex] = 40 x 0.5578 = 22.3 years would have passed for her
This means that she'll be 20 + 22.3 = 42.3 years old