Read each description and classify each as an elastic collision or inelastic collision a. Football player catches a football
b. A billiard ball colliding with another billiard ball
c. A train crashing into a plan

Electricity and discharge

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.

D. the index of refraction of the second medium is lower.