An astronaut at rest has a heart rate of 65 beats/min.What will her heart rate be as measured by an earth observer when the astronaut's spaceship goes by the earth at a speed of 0.60 c?
A)39 beats/min
B)52 beats/min
C)108 beats/min
D)81 beats/min

Question

Quizplus · Accepted Answer

Due to time dilation in special relativity, the heart rate measured by the Earth observer will be slower. The time dilation factor is given by the Lorentz factor, which is approximately 0.8 for 0.60c. Thus, the heart rate will be 65 beats/min * 0.8 = 52 beats/min.

An Astronaut at Rest Has a Heart Rate of 65