Question

The question I have, has to do with relativity (or so I think).

Imagine a fighter jet with two pilots travelling at twice the speed of sound.

I would imagine that if the pilot R (rear seat) throws a tennis ball at Pilot F(front seat), it will hit pilot F as the ball was already travelling at mach 2 and it was further boosted by pilot R. (please correct me if I am wrong).

Will it be the same if pilot R shouts at pilot F.(does sound waves act just like the tennis ball relative to the speed of the jet aircraft?)

Answer 1

The question I have, has to do with relativity (or so I think).

Imagine a fighter jet with two pilots travelling at twice the speed of sound. I would imagine that if the pilot R (rear seat) throws a tennis ball at Pilot F(front seat), it will hit pilot F as the ball was already travelling at Mach 2 and it was further boosted by pilot R. (please correct me if I am wrong). Will it be the same if pilot R shouts at pilot F.(does sound waves act just like the tennis ball relative to the speed of the jet aircraft?)

Answer:

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Yes, you are correct about a tennis ball. A fighter jet, with pilots, tennis ball and air inside, acting like a closed inertial reference frame. Physical laws take the same form in all inertial frames, thus in this problem sound waves will act like a tennis bell and pilots can hear each other.

Other situation will be if there are two jet fighters or some plane without cab (see picture bellow). In this case frame isn't closed and air between the pilots doesn't moving with plane, so in this case they can't hear

each other, because speed of sound is the property of the material in which it propagate .