Doppler Effect is required to solve the problem. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. The general formula of observed frequency, due to Doppler's effect is as follows,

= Frequency observed by observer
v = Velocity of Sound
= Velocity of observer
= Velocity of source
= Frequency of source
PART A) Replacing our values we have that,



PART B) Here the same procedure is performed but this time repeated in the opposite direction.



I don’t think I understand the question but true?
Answer:
Average acceleration =-2.53m/s^2
Displacement s = 4.2m
Explanation:
<span>Objects X and Y are in a strong magnetic field.
Both objects are removed from the magnetic field, after which
the magnetic domains in Object X remain unchanged while the
domains in Object Y go from being aligned to becoming random.
Object X is a permanent magnet because it retains the alignment
of the domains, while object Y is a temporary magnet because the
domains became random. (B)</span>