What is the first constant of a spring which its streatched
(A) 2mm by a force of 4N

Ibelieve the answer you're looking for is

Answerthe distance between the two ends of the galaxy is 150,000 light years;

Sounds propagates through some kind of medium. usually it's air, but it goes just as well through solid objects like walls, windows etc. a soundwave will compress the (air)molecules in front of it, and if this increased density wave hits your ears, you register it as sound. solid objects like walls are a lot denser than air, this means that they will damp a wave, but also carry it easier.