Bullets and Gravity

[ewenm]

SystemParanoia said:

http://galileoandeinstein.physics.virginia.edu/mor...

Newtonian mountain

excellent. I shot myself in the back of my head!

[Big E 118]

I don't own a gun but I live in South London so I'm likely to see someone in the street or local post office with a gun fairly soon.

I will stop them and ask them if they would like to resolve an internet forum discussion with a bit of scientific experimentation.

I will (or my next of kin will) notify you of the results.

Edited by Big E 118 on Tuesday 1st June 11:31

Edited by Big E 118 on Tuesday 1st June 11:32

[mat205125]

Mattt said:

Read up on vectors

Justayellowbadge said:

Curvature of the Earth may have a tiny impact as 'horizontal' is a tangent...

An important assumption

[GravelBen]

mattdaniels said:

Did you never do the experiment in science lessons at school using two tennis balls? One rolled off the side of the desk the other dropped? Both hit the floor at the same time.

How accurately/precisely did you measure a) The simultaneous release and b) the moment of impact?

[mat205125]

SystemParanoia said:

EVERYTHNIG falls at 9.81 m/s, the only variable is how much velocity you give it in the horizontal direction.

The force of gravity accelerates everything at 9.81 metres per second squared. The terminal velocity of an object is the speed where this downward accerative force is balanced by the resistive force being applied in the other direction by the air resistance in the earth's atmosphere .... A hammer will fall faster than a feather on the earth, however in a vacuum, but will accerate at identical rates, and never reach a terminal velocity - they will still be accelerating when they hit the ground.

[SystemParanoia]

hehe, thats what i ment...

now wheres that dunce hat

[Engineer1]

The Monkey and Hunter experiment shows this reasonably well.
here

[Monkey boy 1]

I presume that the timing of the bullet being dropped vertically would have to coincide with the exit of the bullet from the end of the barrel of the weapon its fired from, not from when the trigger is pulled.

[sinizter]

Monkey boy 1 said:

I presume that the timing of the bullet being dropped vertically would have to coincide with the exit of the bullet from the end of the barrel of the weapon its fired from, not from when the trigger is pulled.

Yes. But with a real gun, the exit velocity will be high enough that the time spent in the barrel will have a negligible effect.

[mat205125]

sinizter said:

Monkey boy 1 said:

I presume that the timing of the bullet being dropped vertically would have to coincide with the exit of the bullet from the end of the barrel of the weapon its fired from, not from when the trigger is pulled.

Yes. But with a real gun, the exit velocity will be high enough that the time spent in the barrel will have a negligible effect.

even if one were a pistol, and the other a rifle?

[SystemParanoia]

http://techtv.mit.edu/videos/735-monkey-and-a-gun

MIT for the win

[sinizter]

mat205125 said:

sinizter said:

Monkey boy 1 said:

I presume that the timing of the bullet being dropped vertically would have to coincide with the exit of the bullet from the end of the barrel of the weapon its fired from, not from when the trigger is pulled.

Yes. But with a real gun, the exit velocity will be high enough that the time spent in the barrel will have a negligible effect.

even if one were a pistol, and the other a rifle?

How much extra time is a bullet spending in the barrel of a rifle compared to a pistol ?

If you could find that out, I will calculate the difference and let you know.

[WorAl]

now you are getting into seriously confusing territory as pistol rounds don't travel as fast as rifle rounds (in most cases) but also, you can have different velocities for the same size caliber.

[louiebaby]

SystemParanoia said:

http://techtv.mit.edu/videos/735-monkey-and-a-gun

MIT for the win

I love Physics...

[Bibbs]

sinizter said:

How much extra time is a bullet spending in the barrel of a rifle compared to a pistol ?

If you could find that out, I will calculate the difference and let you know.

For the SA80 ..

Muzzle velocity : 894m per second.
Barrel length : 518mm

So the answer is "not long".

[s3fella]

Does rifling on a gun barrel produce any sort of "lift" on a bullet, or does the spinning action do quite the opposite, it destroy any aerodynamic lift?

[Johnnytheboy]

I wouldn't expect it to make a jot of difference.

[tribbles]

s3fella said:

Does rifling on a gun barrel produce any sort of "lift" on a bullet, or does the spinning action do quite the opposite, it destroy any aerodynamic lift?

It'll even out any differences in the manufacture of the bullet - by having the bullet spinning, any imperfections which would cause an aerodynamic effect (extra drag) wouldn't be in the same angular position, so it'll be pushed upwards, leftways, downwards, rightways, upwards ....

[sinizter]

s3fella said:

Does rifling on a gun barrel produce any sort of "lift" on a bullet, or does the spinning action do quite the opposite, it destroy any aerodynamic lift?

No lift or reverse.

Whatever the spin is doing at the 'top' of the bullet, it is doing the opposite at the 'bottom'

[Bibbs]

s3fella said:

Does rifling on a gun barrel produce any sort of "lift" on a bullet, or does the spinning action do quite the opposite, it destroy any aerodynamic lift?

Keeps it straight. That's it. Stops it tumbling through the air.

The aiming above the target for the bullet to "drop" onto is done by adjusting the sight (on the SA80 is was a dial you spun round dependant on distance - this would lower or raise the rear of the sight, changing your aim).

Have you ever shot a paintball over a long distance? They get to a few 100 meters and then deflect massively in a random direction. The balls spin out of axis due to the smooth barrel then as they slow with wind resistance, the spin causes them to fly about.

Edited by Bibbs on Tuesday 1st June 14:11