I believe thye answer is either d or c
The observed differences in amplitudes are due to interference between the sound waves. The decrease in amplitude is due to destructive interference of the waves and the increase in amplitude is due to constructive interference.
The answer would B, trust me it’s right
Wending your way through this question and the list of choices
is like running through a corn-maze on a moonless night with
your eyes closed.
Work = (force) x (distance)
Keeping with the units used In the question ...
Work = (90 pounds) x (4 feet) = 360 foot-pounds .
If you want the work expressed in joules, then you need to convert
pounds and feet to newtons and meters.
(90 pounds) x (4.448 newtons/pound) = 400.32 Newtons
(4 feet) x (1 meter / 3.28084 feet) = 1.219 meters
Work = (force) x (distance)
= (400.32 newtons) x (1.219 meters) = 488.1 joules .