Another weird question I thought up :D

[Latrobe]

The weird things I think of when I'm bored. This poped into my head one day while thinking how fast a .50 cal would leave the barrel of a gun on a P-51 flying 350 mph. (That isn't the question    )

Question: Let's say a bullet leave the barrel of the rifle at 2,300 ft/s. Now, everyone fires their rifles at a standing, crouch, or prone position, so they are not moving in any direction. Let's take that same rifle (fires at 2,300 ft/s), and put it on a rig that can move at 2,300 ft/s, but in the opposite direction that the barrel faces. What would happen to the bullet if you fired it at 2,300 ft/s one way (let's make it right --> ), and just as you fired the rifle was moving in the opposite direction at 2,300 ft/s (which is left <-- ).

Would the bullet stay right at the spot you fired? Would it have no effect on the bullet whatsoever? Would the bullet travel at a slower speed?

<--Gun(2,300 ft/s)      Bullet(2,300ft/s)-->

[Strip]

Bullet would stay in the exact spot it was fired in.

However if you do the same to a laser ie...

<-----source 186,600 miles per second....viewer stationary......light 186,600 miles per second----->

The viewer would see the light traveling 186,600.

Thank Einstein for that revelation.

[oakranger]

Bullet would stay in the exact spot it was fired in.

However if you do the same to a laser ie...

<-----source 186,600 miles per second....viewer stationary......light 186,600 miles per second----->

The viewer would see the light traveling 186,600.

Thank Einstein for that revelation.

But what about the kick back, or recoil of the rifle?  That bullet is be projected out of that barrel by explosion and expansion of gases in the barrel.  How is that being taken away as the rifle goes opposite direction at the same ft/sec?

[Latrobe]

But what about the kick back, or recoil of the rifle?  That bullet is be projected out of that barrel by explosion and expansion of gases in the barrel.  How is that being taken away as the rifle goes opposite direction at the same ft/sec?

That's what got me thinking. If it was just a spring (ya right) that pushed the bullet out at 2,300 ft/s then off course the bullet would go anywhere. However, bullets are propeller by a controlled explosion in the gun and the gases that come from that explosion.

[phatzo]

some very basic Newton
every action has an equal and opposite reaction the kick back would increase the speed of the gun.

[1701E]

So, what if you calculated how much recoil the rifle will cause, and slow the gun to the speed minus that recoil speed, so when the gun fires it kicks it up to 2,300?

Rifle speed in backwards direction (RB)
Recoil (R)
Gun (G)
Bullet (B)

R = 20FP/S
RB = 2,300FP/S

RB - R = 2,280 (SRB)

Set SRB to 2,280FP/S, when fired G will accelerate to full RB due to R, causing G to go 2,300FP/S one direction as B goes 2,300FP/s in the other.

Just using random Recoil number, but you get the idea.  Not sure if it would work, but being 4am and all, I get weird ideas.

[phatzo]

but you need to take mass into account
edit also entropy

food for thought

http://video.google.com/videoplay?docid=-837913422945616421

[rpm]

If you are talking about firing a "tail gun", the bullet loses thrust equal to the speed the gun is travelling. That's one of the reasons tail guns were removed from modern bombers. The bullets would "fall off" at a significant rate and were ineffective against fighters.

[bcadoo]

If you are talking about firing a "tail gun", the bullet loses thrust equal to the speed the gun is travelling. That's one of the reasons tail guns were removed from modern bombers. The bullets would "fall off" at a significant rate and were ineffective against fighters.

To the tail gunner the bullet appears normal.  And any intercepting fighter's speed is added to the kinetic energy of the bullet. (Imagine if you dropped a box of bullets into the path of an SR-71 going mach 3.)

[Treize69]

If you are talking about firing a "tail gun", the bullet loses thrust equal to the speed the gun is travelling. That's one of the reasons tail guns were removed from modern bombers. The bullets would "fall off" at a significant rate and were ineffective against fighters.

Actually they were removed because you can't shoot down missiles with a tail gun, and the wind behind the bullet actually increases its range relative to the aircraft- a tail gun reaches farther than a nose gun.

[oakranger]

So, what if you calculated how much recoil the rifle will cause, and slow the gun to the speed minus that recoil speed, so when the gun fires it kicks it up to 2,300?

Rifle speed in backwards direction (RB)
Recoil (R)
Gun (G)
Bullet (B)

R = 20FP/S
RB = 2,300FP/S

RB - R = 2,280 (SRB)

Set SRB to 2,280FP/S, when fired G will accelerate to full RB due to R, causing G to go 2,300FP/S one direction as B goes 2,300FP/s in the other.

Just using random Recoil number, but you get the idea.  Not sure if it would work, but being 4am and all, I get weird ideas.

I never took physice class but looks like you know what you are talking about. 

This is like the quesion i remember hearing on speed.  If a train was going at the speed of light, and you are in the train running the same direction.  Are you going fast then the speed of light?

[Strip]

But what about the kick back, or recoil of the rifle?  That bullet is be projected out of that barrel by explosion and expansion of gases in the barrel.  How is that being taken away as the rifle goes opposite direction at the same ft/sec?

So, what if you calculated how much recoil the rifle will cause, and slow the gun to the speed minus that recoil speed, so when the gun fires it kicks it up to 2,300?

Rifle speed in backwards direction (RB)
Recoil (R)
Gun (G)
Bullet (B)

R = 20FP/S
RB = 2,300FP/S

RB - R = 2,280 (SRB)

Set SRB to 2,280FP/S, when fired G will accelerate to full RB due to R, causing G to go 2,300FP/S one direction as B goes 2,300FP/s in the other.

Just using random Recoil number, but you get the idea.  Not sure if it would work, but being 4am and all, I get weird ideas.

When you measure fps you taking into account the recoil of the rifle. Providing at least you use the same method to hold the rifle between firings. So you dont need to add or subtract speed for recoil effects. Even so its usually less than 1 fps which is really unmeasurable in most systems.Remember speed is relative.....your doing hundreds of mph sitting in your chair right now. If you sit at a bench and fire 2300 fps youll get 2300 fps moving backwards at the same rate. In fact most recoil takes place after the bullet has left the barrel leaving no recoil in the bullet speed equation. I fire a 300 Ultra Mag that kicks a 200 grain bullet 3000 fps and doesnt move a millimeter. No recoil....you can hold your finger on the trigger and fire it without touching the rest of the gun.

Strip

[Shuffler]

But what about the kick back, or recoil of the rifle?  That bullet is be projected out of that barrel by explosion and expansion of gases in the barrel.  How is that being taken away as the rifle goes opposite direction at the same ft/sec?

It is not..... The bullet started at minus speed and the explosion would push it from minus to zero. In fact making it stop while the gun moved off of it.

[Yossarian]

Would the bullet stay right at the spot you fired? Would it have no effect on the bullet whatsoever? Would the bullet travel at a slower speed?

<--Gun(2,300 ft/s)      Bullet(2,300ft/s)-->

It depends how you look at it.

From the perspective of the gun, the bullet would move away at 2300+2300=4600 feet per second (according to an observer travelling with the gun).

From the perspective of the bullet, the gun would move away at 2300+2300=4600 feet per second (according to an observer travelling with the bullet).

From the perspective of the place from which the gun was fired (presumably a stationary point on the surface of the Earth), then the bullet would be stationary relative to that point.

[Strip]

It depends how you look at it.

From the perspective of the gun, the bullet would move away at 2300+2300=4600 feet per second.

From the perspective of the bullet, the gun would move away at 2300+2300=4600 feet per second.

From the perspective of the place from which the gun was fired (presumably a stationary point on the surface of the Earth), then the bullet would be stationary.

This is incorrect if I am reading it right.......speed is relative.

From the perspective of the gun, the bullet would move at 2,300 fps and in essesence stop moving in relation to its surroundings.

From the perspective of the bullet the gun would move away at 2,300 and  the bullet itself would be at rest in its surroundings.

I agree with the last one.....