If you place a plane mirror vertically into water, and a dolphin moves toward it with a speed of 4 m/s, she will see her image move toward her at a relative speed of
A) 6. m/s.
B) 2. m/s.
C) 4. m/s.
D) 10. m/s.
E) 8. m/s.

Question

Quizplus · Accepted Answer

The image in a plane mirror appears to move at the same speed as the object. Since the dolphin moves toward the mirror at 4 m/s, the image also appears to move toward the dolphin at 4 m/s. The relative speed between the dolphin and her image is the sum of their speeds, which is 4 m/s + 4 m/s = 8 m/s.

If You Place a Plane Mirror Vertically into Water, and a Dolphin