Imagine Bob is on the earth and Mary is traveling past the earth with a speed of
ID: 1986240 • Letter: I
Question
Imagine Bob is on the earth and Mary is traveling past the earth with a speed of 8500 m/s. A meteor moving in the same direction as Mary passes her. Bob observes the meteor's speed to be 15700 m/s. What is the speed of the meteor as measured by Mary?Now suppose that according to Bob Mary's speed is 1.41 ×108 m/s and the meteor speed is 2.00 ×108 m/s. What is the speed of the meteor that Mary measures now?
Suppose that Bob sees a gamma ray instead of a meteor passing Mary. A gamma ray is a form of electromagnetic radiation; so Bob measures the speed of the gamma to be the speed of light. What speed does Mary measure?
Explanation / Answer
1st case: the speed of the meteor as measured by Mary =meteor's speed wrt earth-speed of mary =15700 m/s- 8500 m/s=7200m/s. 2nd case: speed of the meteor that Mary measures now =meteor speed wrt bob-mary speed wrt bob =2*108-1.41*108=63.72m/s 3rd case: mary measure it same as speed of light as her speed can be neglected when compared to speed of light