An observer on the ground will hear a sonic boom from an airplane travelling faster than the speed of sound:

Only when the plane breaks the sound barrier.

When the plane is directly overhead.

An observer on the ground will hear a sonic boom from an airplane trav

1.	An observer on the ground will hear a sonic boom from an airplane travelling faster than the speed of sound:
A.	Only when the plane breaks the sound barrier.
B.	As the plane is approaching.
C.	When the plane is directly overhead.
D.	After the plane has passed by.
Answer» B. As the plane is approaching.