During the winter Olympic biathlon trials, Eric is shooting his rifle at a target. What is the de Broglie wavelength of a 10.0-g bullet fired from the rifle at 500. m/s

Answer(b) both involve the use of levers;

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.