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.

How is coal extracted from mountaintop removal mines? a. dynamite is used to create underground tunnels where miners go to extract the coal. b. dynamite is used to break apart rocks and then draglines are used to remove the broken rock and reach the coal. c. coal in mountaintops is extracted by digging strips in the landscape to reach the coal. d. placer deposits in mountain river bottoms are removed by

In an experiment, how can i change human errors? be specific.

What’s #16 asking and how do i solve it?