Which of these events is an example of the Doppler shift? A. The amplitude of a wave on a string increases as the frequency decreases.
B. The amplitude of sound from a tuning fork decreases due to damping.
C. The frequency of light from a star increases as it moves toward us.
D. The intensity of an electromagnetic wave increases with the field strength.
E. The velocity of an electromagnetic wave changes as its medium changes.

On a horizontal frictionless surface, a small block with mass 0.200 kg has a collision with a block of mass 0.400 kg. immediately after the collision, the 0.200 kg block is moving at 12.0 m/s in the direction 30° north of east and the 0.400 kg block is moving at 11.2 m/s in the direction 53.1° south of east. use coordinates where the +x-axis is east and the +y-axis is north.(a) what is the total kinetic energy of the two blocks after the collision (in ) what is the x-component of the total momentum of the two blocks after the collision? (indicate the direction with the sign of your ) what is the y-component of the total momentum of the two blocks after the collision? (indicate the direction with the sign of your answer.)