If you fired a bullet in a desert...

[BulgarianPride]

Interesting...
I will need give a thought or two.

isn't it around 11km/s? escape velocity, in other words. the usual 300km altitude 'stable' orbits are slower as gravity obeys the law of inverse squares. but as the surface of the earth is what, 5000km from the core, another 300km isn't actually all that big a difference? standard orbits are around 8k/ms I think.
.

Sounds right as i get around 8km/s as escape velocity as well. This is because the bullet is fired horizontally. If the velocity is bigger than 8km/s it would leave orbit.

I've made the mistake thinking that it would hit me in the back 0.55 seconds later.

So golden ratio, you need a gun that can fire at about 8km/s.

 

[Joycee Banercheck]

Got it.
In order to always stay in orbit, the centripetal force acting on the bullet must the force of gravity.

F=m*v^2/r

where m is the mass of the bullet, v is it's velocity and r is the distance from the center of the earth (approximately 6 378 101.5 meters if i fire from 1.5 meters above the ground). Now for the the bullet to be always in orbit, it must travel at

v=(9.8*6378101.5)^0.5=7906.035 m/s

This is the limit, any faster and it will leave earth for good.

In order for the bullet to comeback and hit me in the back it must travel 2*pi*r meters.
so the speed that it must come out is,

v=2*pi*r/0.553 = 72 467 981.25 m/s

Sadly if this bullet is fired from 1.5 meters above the ground , it would leave the earth.
I've probably made a mistake...

I aspire to get this... and soon I will. Maths is cool.

 

[BulgarianPride]

Got it.
In order to always stay in orbit, the centripetal force acting on the bullet must the force of gravity.

F=m*v^2/r

where m is the mass of the bullet, v is it's velocity and r is the distance from the center of the earth (approximately 6 378 101.5 meters if i fire from 1.5 meters above the ground). Now for the the bullet to be always in orbit, it must travel at

v=(9.8*6378101.5)^0.5=7906.035 m/s

This is the limit, any faster and it will leave earth for good.


In order for the bullet to comeback and hit me in the back it must travel 2*pi*r meters.
**ignore everything after this**
so the speed that it must come out is,

v=2*pi*r/0.553 = 72 467 981.25 m/s

Sadly if this bullet is fired from 1.5 meters above the ground , it would leave the earth.
I've probably made a mistake...

I aspire to get this... and soon I will. Maths is cool.

It's just basic physics. Nothing special.
<a class="postlink" href="http://en.wikipedia.org/wiki/Centripetal_force" onclick="window.open(this.href);return false;">http://en.wikipedia.org/wiki/Centripetal_force</a>

 

[1.618034]

Interesting...
I will need give a thought or two.

isn't it around 11km/s? escape velocity, in other words. the usual 300km altitude 'stable' orbits are slower as gravity obeys the law of inverse squares. but as the surface of the earth is what, 5000km from the core, another 300km isn't actually all that big a difference? standard orbits are around 8k/ms I think.

-- Sat Nov 06, 2010 1:05 am --

Ah. Chaos. Where would we be without it?

That applet won't work... Grr.

it's not that special, it's just lets you set the height, attitude and velocity and visualises the parabolas in 'real time'.

Beautifully not that special?

Would be interesting and possibly useful... No worries. I'll have a look elsewhere. But if you see anything similar I'd be interested.

I like this kind of thing... eg: <a class="postlink" href="http://www.cut-the-knot.org/content.shtml" onclick="window.open(this.href);return false;">http://www.cut-the-knot.org/content.shtml</a>

-)

It might work at Work...

 

[BulgarianPride]

....

 

[Joycee Banercheck]

I aspire to get this... and soon I will. Maths is cool.

It's just basic physics. Nothing special.
<a class="postlink" href="http://en.wikipedia.org/wiki/Centripetal_force" onclick="window.open(this.href);return false;">http://en.wikipedia.org/wiki/Centripetal_force</a>

I know. I'm getting there.

 

[1.618034]

isn't it around 11km/s? escape velocity, in other words. the usual 300km altitude 'stable' orbits are slower as gravity obeys the law of inverse squares. but as the surface of the earth is what, 5000km from the core, another 300km isn't actually all that big a difference? standard orbits are around 8k/ms I think.
.

Sounds right as i get around 8km/s as escape velocity as well. This is because the bullet is fired horizontally. If the velocity is bigger than 8km/s it would leave orbit.

I've made the mistake thinking that it would hit me in the back 0.55 seconds later.

So golden ratio, you need a gun that can fire at about 8km/s.

I'll get on it!

Good work.

 

[persvenality cult]

how does a round ball change profile?

All I mean is, it changes shape in a (mathematically) strange ways when it's kicked. At the simplest level, the point of impact is squashed up towards the leading edge, then the front accelerates out, and the remaining energy is spread throughout the ball, altering the shape. This changes how it travels through the air, as does the spin.

I wish I could find a video to show you what I mean.

my only real relevant experience is of how cymbals deform when they hit; there are an (infinite series of) 'modes' by which the energy travels accross the surface in ripples.

and so on. the football has a series of seams and panels, a valve and so on you can sort of get different 'harmonics' by hitting different parts of the construction.


tbh it has very little to do with bullets, they go to great lengths to avoid this sort of deformation in the firing of the bullet, but it is there... just.

 

[MCC]

Ideally the bullet would take a huge ricochet and rip through Gary Neville`s scrotum before nestling nicely up Trace Neville s minge.

 

[yerwot?]

got it now,an extreme example is a golf ball hit hard ,flattens and reforms . i was thinking on the lines of a musket ball.Been an interesting thread considering it was born out of boredom and nurtured on indifference,bit like some of our youngsters on here