The frequency of the sound waves detected by a detector is exactly equal to the frequency of the sound waves emitted by a source. what can we say about the relative motion of the detector and source?

a.
both are at rest.
b.
both are moving with the same velocity.
c.
they are moving with opposite velocities.
d.
both are either at rest or moving with the same velocity.

Choose the most likely outcome of this scenario: jen decided to go bike riding without a helmet. while no one is around during her ride, she is thrown from her bike when her wheel goes into a pothole. she is not injured, but she is terrified to get back on her bike. what happens next? a. her physical health is affected even though she wasn't hurt. b. her mental and emotional health are affected because she is afraid to get back on her bike. c. her social health is affected because she is worried her friends saw the fall. d. her overall health is not affected at all by her fall.