Mort stands on Earth. Velma moves away from him in a rocket, at 299,000 km/s (1000 km/s slower than lightspeed). Mort sends a laser beam toward Velma. As the tip of the beam passes her rocket, Mort observes
A) the beam moving just 1000 km/s faster than Velma.
B) the beam moving away at 300,000 km/s.
C) Both of the above.
D) the beam moving 300,000 km/s faster than Velma.
E) All of the above.

Question

Quizplus · Accepted Answer

The beam moves at the speed of light relative to both Mort and Velma. So, Mort observes the beam moving at 300,000 km/s, and Velma observes the beam moving at 300,000 km/s. Since Velma is moving away from Mort at 299,000 km/s, Mort observes the beam moving just 1000 km/s faster than Velma.

Mort Stands on Earth