Time dilation: A spaceship approaches the earth with a speed 0.50c. A passenger in the spaceship measures his heartbeat as 70 beats per minute. What is his heartbeat rate according to an observer that is at rest relative to the earth?
A) 69 beats per minute
B) 73 beats per minute
C) 65 beats per minute
D) 61 beats per minute
E) 80 beats per minute

Question

Quizplus · Accepted Answer

Time dilation causes the heartbeat rate to appear slower to an observer at rest relative to the earth. The time dilation factor is given by the Lorentz factor, which is approximately 1.15 for a speed of 0.50c. Thus, the heartbeat rate is 70/1.15 ≈ 61 beats per minute.

Time Dilation: a Spaceship Approaches the Earth with a Speed