# Question: A spaceship containing an astronaut travels at a speed of

A spaceship containing an astronaut travels at a speed of 0.60c relative to a second inertial observer.

(a) Who measures proper time intervals in the ship and the proper length of the ship: (1) the astronaut in the ship, (2) the second observer, or (3) neither?

(b) How much time does a clock on board the spaceship appear to lose in a day, according to the second observer?

(c) If the second observer measures a length of 110 m for the ship, what is its “proper” length”?

(d) What is the total energy of the astronaut according to the astronaut if her mass is 70 kg?

(e) Repeat part (d) from the viewpoint of the second inertial observer.

(a) Who measures proper time intervals in the ship and the proper length of the ship: (1) the astronaut in the ship, (2) the second observer, or (3) neither?

(b) How much time does a clock on board the spaceship appear to lose in a day, according to the second observer?

(c) If the second observer measures a length of 110 m for the ship, what is its “proper” length”?

(d) What is the total energy of the astronaut according to the astronaut if her mass is 70 kg?

(e) Repeat part (d) from the viewpoint of the second inertial observer.

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