वेग v से गतिमान विराम द्रव्यमान m0 वाले एक आपेक्षिकीय कण की गतिज ऊर्जा होगी:

Which of the following represents Albert Einstein's famous mass-energy equivalence equation (where E is energy, m is mass, and c is the speed of light in a vacuum)?

Ravi and Swati are twins. Swati travels away into space and returns, separating from Ravi at a relative speed of 0.80c. Ravi and Swati each send out a radio signal once a year according to their own clocks. If Ravi's clock records 15 years for the trip, how many signals does Ravi receive from Swati during this period?