# Question

An astronaut in a spacecraft moves past a field 100 m long (according to a person standing on the field) and parallel to the field’s length at a speed of 0.75c.

(a) Will the length of the field, according to the astronaut, be (1) longer than 100 m, (2) equal to 100 m, or (3) shorter than 100 m? Why?

(b) What is the length as measured by the astronaut?

(c) Which length is the proper length?

(a) Will the length of the field, according to the astronaut, be (1) longer than 100 m, (2) equal to 100 m, or (3) shorter than 100 m? Why?

(b) What is the length as measured by the astronaut?

(c) Which length is the proper length?

## Answer to relevant Questions

The proper lifetime of a muon is 2.20μs. If the muon has a lifetime of 34.8 μs according to an observer on Earth, what is the muon’s speed, expressed as a fraction of c, relative to the observer? The distance to Planet X from Earth is 1.00 light-year. (a) How long does it take a spaceship to reach X, according to the pilot of the spaceship, if the speed of the ship is 0.700c relative to X? (b) How long does it take ...How fast must an object travel for its total energy to be (a) More than its rest energy and (b) More than its rest energy? A proton moving with a constant speed has a total energy 3.5 times its rest energy. What are the proton’s (a) Speed, (b) Kinetic energy, and (c) Momentum? A boat can make a round trip between two locations, A and B, on the same side of a river in a time t if there is no current in the river. (a) If there is a constant current in the river, the time the boat takes to make the ...Post your question

0