Classical Electrodynamics
Physics 6561
Homework 1. Due: In class on Tuesday, 9/9 in class
1. The twin paradox
(Problem 11.6 from Jackson)
Assume that a rocket ship leaves the Earth in year 2100. One of a set of twins born in
2080 remains on the Earth, the other rides the rocket.
The rocket ship is so constructed
that it has an acceleration
g
in its own rest frame (this makes the occupant feel at home).
It accelerates in a straight line path for 5 years (by its own clocks), decelerates at the same
rate for 5 more years, turns around, accelerates for 5 years, decelerates for 5 years and lands
on Earth. The twin in the rocket is obviously 40 years old.
(a) What year is it on Earth?
(b) How far away from the Earth did the rocket ship travel?
(c) (Not in Jackson) How should the driver of the rocket ship change the mass of the rocket
in the initial accelerating phase by releasing fuel in order to feel the constant acceleration
g
in the spaceship? Assume, that the fuel released has a constant velocity
w
relative to the
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 Fall '08
 LIPSON/POLLOCK
 Special Relativity, Ji, rocket ship, lorentz group

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