"... Examination of the F11F established there were three hits—in the windshield, the right engine intake, and the nose cone. The engine's inlet guide vanes were struck, and a battered 20mm projectile was found in the first compressor stage..






 

It will go as fast as any normal bullet would. In the case of the 20mm Vulcan, wiki says 3,450 feet per second. It isn't 3450 + the speed of the plane. You initially get the speed of the plane and then the speed of the bullet , but the bullet starts to slow down the moment it leave the barrel - and especially if the plane speeds up, it can hit the plane. By comparison,  Mach 2 is about 2200 feet per second.

But yes, if the plane is going faster than the bullet, then the bullet will hit the plane. The bullet is only accelerating until it reaches the end of the barrel.

Here is an account of a pilot who shot his own plane in a dive in the 50s. His bullets I think were slower than the modern Vulcan, though.
http://www.check-six.com/Crash_Sites/Tiger138260.htm

Here is a Mythbusters video showing what would happen if you shot a bullet out of a plane backwards and were going as fast as the bullet. The bullet would leave the barrel because of the pressure, but then this happens:

This thread occurs, and yet polls about IQs on here are consistently skewed a deviation or two to the right.  Non sequitur.

An Aggie said it!

/thread

Projectiles fired from a canon are not the same as light.



Light behaves much differently than objects which follow the Newtonian subset of physics.



The speed of light remains the same despite the speed of any object it is traveling.



 

Mach 2 is rougly 2k fps, depending on some variables.

Ah, but consider firing a the same gun from inside the plane facing rearward. Is would still appear to travel at 2000fps right? That's because the plane is traveling at 2000fps, while the bullet remains static. Correct?

Only if the cannon fires a laser beam instead of a projectile.



 

Also only if the cannon is actually a fricken shark with fricken laser beams.

Now, if you had instead asked about a spaceship traveling at the speed of light turning on its headlights, that would have been an interesting question

Warp  2          that was easy

OOPS - I converted a M/S vs MPH in a calculator. My bad.

 

When you are running and you throw a ball forward do you run into the ball?

ETA: Planes can only run into their own ordinance if they accelerate enough after they fire it or the bullet has slowed enough to overtake it.

It would seem that if the conditions the OP postulates obtain then it would be a well understood phenomenon, especially by the worlds various air forces and fighter pilots.

It's simply not how it works.

A projectile that has a charge giving it a mv of x when fired from a barrel on the ground doesn't exit a barrel at x*2 when fired from a moving platform.

Seriously OP?

Whenever I spit out the window I run into it!  

It happens.

Bullet travels @ 2K fps relative to the cannon.  So when the 20mm HEI hits the back wall of the cockpit, the plane blows up, killing our intrepid experimenter.  Thanks a bunch!

Yes

Shit happens when you throw like a girl.

OK - that's right. You do get the extra speed initially. But they loose velocity as soon as the exit the barrel. If you were traveling faster than the bullet can fly it will still exit the barrel (the pressure forces it out, speed isn't a factor). But the plane can travel fast enough to over take it shortly after. Per my link a an example of it happening.

I think you fail to understand the concept of frame of reference.

are you suggesting that if my aircraft was flying at a velocity of 2799 fps and I fired my cannon at 2800 that the bullet would exit the barrel and move off at ONE fps?

 

can you picture how wrong that is?

Holy derp batman. Put the keyboard down. You are making an ass of yourself. If a cop was on the side of the road and radar gunned the ball after being pitched forward from the moving truck what speed would it read? Are you seriously saying 70 mph?



 

With Respect To the cannon.  The motion of the cannon relative to the Ground Observer is significant in this mental exercise.  Vectors, how's dey work, anyhow?

EDIT:  Thread has provided a much need laugh here.  While confusing to some, thinking about relative motion is legit and I hope all the peeps in this thread make sense of it.

All of this would be interesting at speeds approaching C (3E8).  Otherwise it is Newtonion and only interesting in the amount of ignorance it brings to the surface.  

where are you standing?

say for example you are in a aircraft traveling at 500MPH.  

Nolan Ryan is at the rear of the aircraft (inside the aircraft, for the dense people here...)
you are at the front of the aircraft (inside the aircraft, for the dense people here...)

Nolan winds up and throws a 90MPH fastball towards you.

how fast is the baseball traveling?  

to the observers seated in the aircraft, the baseball is traveling at 90MPH.  (in fact, inside the aircraft you could measure this with a standard issue radar gun.)
one would say that these observers are in one reference plane, one which is moving along with the aircraft.

to the observers on the ground, that same baseball is traveling at 590MPH. (500+90MPH)
one would say that these observers are in another reference plane, one which not moving along with the aircraft.

suppose you and Nolan Ryan exchange positions; he's at the front of the aircraft, you are at the rear.
again, he throws a 90MPH fastball at you.  

to the observers seated in the aircraft, the baseball is traveling at 90MPH.  

to the observers on the ground, that same baseball is traveling at 410MPH. (500-90MPH)

suppose you and Nolan Ryan exchange positions AGAIN; he's is once again at the rear of the aircraft, you are at the front.
again, he throws a 90MPH fastball at you.  this pitch is high, though.  

you duck out of the way, and the baseball sails through the open cabin door and then goes straight through the aircraft windshield.

(let's ignore for the moment the fact that the glass slowed the baseball somewhat)

at the moment the baseball comes out the front of the aircraft, how fast is it traveling?  

hint: you already know the answer from this post.

now go re-read your question above.

ar-jedi

It would only be true if somehow the plane accelerated to the same speed from zero relative during the time the bullet was in the barrel.

 

What the hell are you talking about?

Semantics.

your own video shows you to be wrong

I' having a hard time seeing how could it be otherwise?   If the pilot dropped the bullet out of the window of the aircraft at 750Mph, what is the velocity of the bullet relative to a ground observer?

You can not possibly be this stupid.

I'll try to dumb it down for you even more.

The plane is moving at the speed of X (for the sake of argument lets call X a thousands miles an hour, but it can be 500, 2000, 4, 10,000, or 10,000,000 it doesn't matter).  The gun is in the plane.  So the gun is also moving at X because it is in the plane.  Are you with me so far?  The bullet is in the gun.  The gun as we have established is moving at X therefor the bullet, being in the gun, must also be moving at X.  Understand?  Now the bullet, which is already moving at X, is fired.  It has a muzzle velocity of Y (let's call Y 2,000 feet per second, but again, it does not matter).  So the bullet which is ALREADY moving at X is pushed forward from its STARTING SPEED of X at the rate of Y.  So the bullet's speed relative to the plane,which is also moving at X, is only Y, or in this case 2,000 feet per second, but to the ground it is moving at X+Y, or 1,000 miles an hour PLUS 2,000 feet per second.

Now,do an experiment.  Get on your bike and peddle as fast as you can, faster than you can gently throw a tennis ball, now while you are moving, gently throw a tennis ball, come back and tell us what happened.

What will happen is that from your perspective the tennis ball was gently thrown, moved away from you as normal, and bounced off the ground, from an observers perspective who was not moving the ball was moving like a pro tennis serve and smacked off the ground at high speed because itwas moving at the speed of the bike, PLUS the speed of the throw.

Get it yet?

Try another experiment.  Get on the bus and while its moving at 40ish miles per hour get up, and walk toward the front of the bus?  Could you move?  Did you fly out the rear window?  But the bus was moving  at 40 miles per hour and you were moving at just 1.5, how could that be?  Because before you got out of your seat, you were ALSO going 40 miles per hour, so when you got up you were moving at 1.5 miles per hour relative to the bus, which to you, since you are also going 40  miles per hour, is stationary, but to an observer standing watching, your speed was 41.5 miles per hour, or the speed of the bus PLUS the speed you were walking, so you were actually walking FASTER than the bus.

Understand yet?

You are missing the concept of vectors. A vector includes the magnitude (in this case the velocity) and direction.  When an object is launched forward in the same direction of the vehicle then you add the velocities.  When the object is launched backwards like in the video, you still add the velocities, but the object is moving in the negative direction (thus subtracting). If a car is moving at 10 m/s and a ball is thrown backwards at 10 m/s, then in the perspective of a person on the sidewalk the ball will only bounce up and down instead of rolling in any direction.  10 + (-10) = 0

Only relative to an outside observer at 0 MPH.


Think of it another way.  Say a plane flies past you on the ground at 750mph and you shoot a bullet that can reach 700MPH at the plane as it moves away..... can your bullet hit the aircraft?   Certainly not.    Now say you are following 100yds behind at 750Mph and you fire your 700Mph bullet at it.  Can you you now hit the plane?   Certainly so.

The video shows what happens if you shot it backwards - not forwards. In that case IIRC the truck shot the ball at 60mph while it traveled at 60mph.  The link explains what happens when you shoot a bullet forwards at high speeds and shows how it is possible to shoot yourself down.

Yes - they are two different things. He mentioned tail gunners flying faster than their bullets, which is why I included the second video.

You're trolling, right?

RIGHT?

You cannot be that dumb.

I hope.

But ok, here ya go.

X = vehicle velocity
Y = gun muzzle velocity
Z = total projectile velocity

X+Y=Z

Simple enough, Einstein?

So,  vehicle velocity = 2000fps.(X)
gun muzzle velocity = 2800fps.(Y)
total projectile velocity = 2000+2800=4800fps (Z)

TADA!

Physics is hard, yo.

So an observer from the ground holding a radar gun would record the projectile having a muzzle velocity of x (2,800 fps, let's say) + y (velocity of the aircraft). So that radar would record a muzzle velocity of 4,800 fps?

I don't think so.

Your avatar is VERY fitting.

It is 4800fps, sherlock.

No, it is not 4,800 fps.

eta.. how the fuck would ground crews ever be able to regulate the guns if they had to take into account the varying speed of the aircraft? Even at 400 mph that would create problems.

Actually, it is. But keep on being wrong. Your choice.

To the plane, the bullet would be moving away at 2800fps.

To the observer, the bullet would be coming towards at 4800fps.

JESUS FUCKING CHRIST. REALLY? REALLLLLLLLLY DOOD?

I'm embarrassed for you.

I AM pretty drunk!

But I'm also right. I think.