Why do sound waves do not travel in empty space ?

a. because sound waves do not need matter to travel.

b. because sound waves need matter to travel.

c. because sound waves need vacuum to travel.

d. none of the above

You are traveling in a car going at a constant speed of 100km/h down a long, straight highway. you pass another car going in the same direction which is traveling at a constant speed of 80km/h. as measured from your car's reference frame this other car is traveling at −20km/h. what is the acceleration of your car as measured from the other car's reference frame? what is the acceleration of the other car as measured from your car's reference frame?

What is the freezing point of radiator fluid that is 50% antifreeze by mass? kf for water is 1.86 ∘c/m.

Photons with the highest energy have the longest period