# Sound barrier

How fast must a human throw a baseball in order to break the sound barrier? I know a jet breaks the sound barrier at approximately 750 mph but would it be the same for a human?

russ_watters
Mentor
The speed of sound in air is the speed of sound in air. It doesn't depend on the object traveling through it.

That is an interesting question, though from the point of view of force. How much force would a ball require to reach the sound barrier? I think the ball might get destroyed, but a way to calculate it might be to think of a sphere of the same weight of the baseball, and shoot it out of a cannon. Whatever force the sphere needs to come out of a cannon by explosion to reach the speed of sound at whatever situation the air is in at that moment
(pressure, etc) could be calculated.

Google says that the speed of sound (depending on air conditions) is 340 meters/second. If a pitcher throws a 100 mile an hour fast ball, Google tells me that's, 44.7 meters/second. I do not know the rules but I think that the forces needed to make something go faster are not linear. But, that's the limit of my knowledge at this moment.

I will admit that one time I got a trap speed for my "fast ball" at thing they had set. I can't remember exactly but I was in teh 50-60 mph range. I seem to remember the number 58. But not sure. I threw as hard as I could, and i'm 5'11" and was not in bad shape. I still find it hard to imagine how anyone could throw a baseball at 100mph.
44.7

K^2
Yes, because at constant acceleration v²=2ad=2Fd/m, you need to quadruple the force to double the final velocity. Even worse, since you want to "pitch" the ball past the sound barrier, you have to deal with significant drag. In fact, the drag is highest right before you break the sound barrier, and the baseball is the wrong kind of shape for going against wave drag that is typical for transonic speeds.

I don't think you'll break the baseball, but you will need a cannon of some sort to fire it at these speeds.

If you were on the ground and an airplane flew over you at 2000ft at Mach1, would the shock wave sound the same as you would hear from an airplane flying over you at 2000ft travelling at Mach2 or Mach3, Mach5 even?

My guess is that it would.
My reasoning being that sound travels at the same speed given same medium/altitude etc. Therefore even though the plane would have a Mach 1,2,3 or 5 pressure wave in front of it, that wave can only propagate at the allowable speed of sound for that medium.
Is this correct?

HallsofIvy
Homework Helper
Yes, that's true. The pressure wave immediately falls behind the plane.

The sonic boom changes at higher speeds as the Mach Cone gets tighter and tighter, which does lead to a more intense sonic boom. Also - you are plowing through more air and expending more energy, which is released in the boom.

cjl
The sound would be very similar, but the intensity of the sound would be very different - at mach 5, the shock wave would be of a much larger magnitude than the shock wave from a plane at mach 1.05.

How fast must a human throw a baseball in order to break the sound barrier? I know a jet breaks the sound barrier at approximately 750 mph but would it be the same for a human?

I want to know about capturing of sound wave how it can be captured? And then distroyed

rcgldr
Homework Helper
If you were on the ground and an airplane flew over you at 2000ft at Mach1, would the shock wave sound the same as you would hear from an airplane flying over you at 2000ft travelling at Mach2 or Mach3, Mach5 even?
I'm not sure it would still be a shock wave after traveling 2000 feet. Shock waves turn into sound waves (sonic booms) over time and distance. A shock wave sounds like a loud crack, while a sonic boom sounds much deeper. In the second part of this video, you'll hear a shock wave as a super sonic F14 does a close flyby:

http://rcgldr.net/real/f14flyby.wmv

sophiecentaur
Gold Member
2020 Award
Yes, because at constant acceleration v²=2ad=2Fd/m, you need to quadruple the force to double the final velocity. Even worse, since you want to "pitch" the ball past the sound barrier, you have to deal with significant drag. In fact, the drag is highest right before you break the sound barrier, and the baseball is the wrong kind of shape for going against wave drag that is typical for transonic speeds.

I don't think you'll break the baseball, but you will need a cannon of some sort to fire it at these speeds.

You're using the word Force - and that's justified if you assume a given length of arm / throwing stroke. But you could use a "cannon' with a very long barrel and achieve whatever exit velocity you wanted with a force equal to your arm's strength. It's really Impulse that counts - Force times time applied.

russ_watters
Mentor
I want to know about capturing of sound wave how it can be captured? And then distroyed
Welcome to PF.

Could you rephrase the question - it sounds like you're looking for a wall.