A Fun Physics Question

[JONTHEBOMB]

At the instant a horizontally held rifle is fired, a bullet held at the rifle's side is released and drops to the ground.  Which bullet strikes the ground first, the one fired from the rifle or the one dropped?

[AtomSmasher]

the answer your looking for is they hit the ground at the same time because gravity pulls them down at the same speed, but if you wanted to look at the actual answer heres a few reasons that come to mind why that wouldn't necessarily be true...the bullet fired doesn't start dropping until after it reaches the end of the barrel so it should hit the ground after the dropped one, plus it has much less mass since it no longer has its shell casing and the gun power so its much more sensitive to wind affecting its movement, an updraft or downdraft could change things dramatically.

[RetroJames]

At the instant a horizontally held rifle is fired, a bullet held at the rifle's side is released and drops to the ground.

[MaximRecoil]

the bullet fired doesn't start dropping until after it reaches the end of the barrel so it should hit the ground after the dropped one, plus it has much less mass since it no longer has its shell casing and the gun power so its much more sensitive to wind affecting its movement, an updraft or downdraft could change things dramatically.

The question only used the term "bullet". A bullet is a bullet; period. Add a case, powder and primer and you have a cartridge.

Either way, the fact that the bullet is being forced through the air at a high velocity will pretty much guarantee that it stays aloft longer than the dropped bullet, especially if you cast the bullet in the shape of a glider. There are all sorts of effects that can happen when an object is moving through the air at high speed, turbulence for example. The air becomes a far stronger secondary force acting on the bullet when it is moving through it horizontally at say 3,000 feet per second, rather than just being dropped.

[DrewKaree]

The air becomes a far stronger secondary force acting on the bullet when it is moving through it horizontally at say 3,000 feet per second, rather than just being dropped.

I can vouch for a field goal attempt demonstrating this, yet I cannot state this for certain, since I wasn't physically there to witness the event, I only watched it on television, which could have been faked as easily as a moon landing on a sound stage somewhere

[Buddabing]

On the moon they would hit at the same time. There was a video clip of an astronaut on the moon (Apollo 15 mission) holding a feather and a hammer and dropping them at the same time. They landed at the same time.

Here's a link to the transcript and video.

[AtomSmasher]

On the moon they would hit at the same time. There was a video clip of an astronaut on the moon (Apollo 15 mission) holding a feather and a hammer and dropping them at the same time. They landed at the same time.

Here's a link to the transcript and video.

Actually I'm betting a normal bullet fired on the moon (assuming it can be fired on the moon even though theres no oxygen) would be at an escape velocity and would never hit the ground

[MaximRecoil]

On the moon they would hit at the same time. There was a video clip of an astronaut on the moon (Apollo 15 mission) holding a feather and a hammer and dropping them at the same time. They landed at the same time.

Here's a link to the transcript and video.

Actually I'm betting a normal bullet fired on the moon (assuming it can be fired on the moon even though theres no oxygen) would be at an escape velocity and would never hit the ground

Not unless you know of any bullets that hit 8,000 FPS or so. Even the fastest wildcat rounds, such as the 50 BMG necked down to 22 caliber only get to the 5,000 FPS range.

[AC.]

Don't forget the curvature of the earth.  The fired one will hit .0001 seconds later, or something. 

[M3talhead]

Don't forget the curvature of the earth.  The fired one will hit .0001 seconds later, or something. 

...assuming the Earth has a perfectly smooth surface, in which case I'd invest in rollerblade manufacturing.

[SirPoonga]

Don't forget the curvature of the earth.  The fired one will hit .0001 seconds later, or something. 

For the distance a bullet travels the curvature of the earth is insignificant.


Ok, a lot of variables involved.
If you take out friction of air and no air currents, assume a perfectly flat area, the distance the bullet flies is in significant to the earth's curvature, the bullet dropped was dropped at the instant the fired bullet left the barrel, and both bullets started at the exact same height, then they would both hit the ground at the same time.  This is becuse gravity is a constant force downward.  Both objects have the same downward force vector, no matter what horizontal force vector there is.  In fact, assume the above conditions the bullet fired will hit the ground with the same horizontal velocity as it had when it left the barrel.

If the answer is that both DO hit the ground at the same time, I would have to see that to believe it.  Is there not a huge variable in the amount of energy released by the casing?  Different bullets fired horizontally will go further than others, there is no way all bullets fired in this way would hit the ground at the same time....

Or did you just blow my mind?

See my above explaination...
I will add, with the above conditions, if you fire multiple bullets you need them to leave the barrels at exactly the same time.   Since there will be different FPS some will have to be fired slightly ahead of others in order for that to happen
But yes, if you fired all at the same time they would all hit the ground at the same time.  The horizontal force from the chemicals has nothing to with the vertical force from the earth.

[JONTHEBOMB]

At the instant a horizontally held rifle is fired, a bullet held at the rifle's side is released and drops to the ground.  Which bullet strikes the ground first, the one fired from the rifle or the one dropped?

I would have to see that to believe it. 

A large vacuum on earth would be needed in order to see or hear the bullets hit at the sametime.

Also, I didn't realize we had Physics Professors on BYOAC.

[DrewKaree]

Okay, I give up.  When do we get to the FUN physics question?

[AC.]

Okay, I give up.  When do we get to the FUN physics question?

'fun' and 'physics' are contradictory terms.   
Unless you are talking about breast implants, or jello wrestling, etc...

[missioncontrol]

mmmmmmmmm

jello wrestling