The variable would be “X”
Hope it helped you.
A. Acceleration is a wrong answer. Acceleration is the rate of change to in velocity. It involves a change in speed and direction.
B. Force is a wrong answer. Force is a directions from push/or pull.
C. Inertia is a correct. Inertia is a tendency of an object to stay at the rest or preserve its state of motion.
D. Velocity is a incorrect answer. Velocity is the placement of an object during a specific unit of time. It has two measurements are needed to determine velocity.
-Charlie
-Thank you so much!
Have a great day!
Answer:
Part a)

Part b)

Explanation:
Part a)
Level of sound = 75 dB
now we know that

here we know that

now we have


Part b)
Intensity of sound wave is given as

here we know that

so we have


now we know



now we have

