Using the Definition of Kinetic Energy, we have:
Sound intensity = 1/(r^2)
That is Sound intensity is indirectly proportional to the distance. Therefore, sound becomes 9 times less intense.
Answer:
From the formula of force:

since AB and k are constants:

x is a constant of proportionality
• when force is 4N, separation distance is 1

therefore, equation becomes

when r is doubled, r becomes 2. find F:

answer would be C. multiply the input force.