Johnx64
[H]F Junkie
- Joined
- Apr 22, 2002
- Messages
- 9,326
Hate_Bot said:
If you shoot a bullet or anything fast enough sideway's you can send it into orbit. But thats gotta be pretty fast
Wait I get that gravity will still slow it down.
![[H]ard|Forum](/styles/hardforum/xenforo/logo_dark.png){kind=logo}
Game Physics
- Thread starter Wrench00
- Start date
If you shoot a bullet or anything fast enough sideway's you can send it into orbit. But thats gotta be pretty fast
Wait I get that gravity will still slow it down.
S0m30n3 said:
The reason gliders fly is hot air currents rising, pushing the glider up
the reason plans fly is because the curve of there wings. The larger curve on top creates lower pressure, while the flatter curve on the bottom creates higher pressure air, which pushes the plane up. It's not defying gravity or anything.
S0m30n3 said:If you shoot a bullet or anything fast enough sideway's you can send it into orbit. But thats gotta be pretty fast
Yes but gravity is STILL effecting it. Even in space, if you are close to a planet gravity still effects it (how do you think satellites orbit the planet?)
Johnx64
[H]F Junkie
- Joined
- Apr 22, 2002
- Messages
- 9,326
Hate_Bot said:
But its using wind resistance to create a force on it. Just like a bullet flying through the air the force from the gun blast is creating a force around the bullet while its traveling and since the force on the bottom is greater due to gravity pulling on it, it should stay in the air longer.
S0m30n3 said:
no because the bullet is uniform in shape, hence air travels all around it equally, hence all forces applied on it are canceled out, hence gravity takes its place.
And gravity pulls things down, the force on the bottom of an airplae wing isn't gravity it's high are pressure. Gravity will never "make something be in the air longer"
what comes up, must come down
Johnx64
[H]F Junkie
- Joined
- Apr 22, 2002
- Messages
- 9,326
"no because the bullet is uniform in shape, hence air travels all around it equally, hence all forces applied on it are canceled out, hence gravity takes its place."
Yes and because gravity is pulling on it the pressure on the lower half of the bullet is greater.
"And gravity pulls things down, the force on the bottom of an airplae wing isn't gravity it's high air pressure. Gravity will never "make something be in the air longer"
Yeah its used to make more pressure to keep that much weight in the air. If it weighs less it wont need that much force to keep it in the air.
Yes and because gravity is pulling on it the pressure on the lower half of the bullet is greater.
"And gravity pulls things down, the force on the bottom of an airplae wing isn't gravity it's high air pressure. Gravity will never "make something be in the air longer"
Yeah its used to make more pressure to keep that much weight in the air. If it weighs less it wont need that much force to keep it in the air.
S0m30n3 said:
Sigh, listen, gravity doesnt create "pressure", it creates "force". Th "force" of gravity pulls the bullet down. I dunno what freaky deaky high school you went to, but gravity never will, and never does, cause something to go up, the reason rockets go into space is because of the tremendous force created by the engines. The reasons planes fly is because of varying air pressure. during all this time gravity IS PULLING THESE THINGS DOWN. WE HAVE NOT YET CREATED A DEVICE THAT SOMEHOW REVERSES THE EFFECTS OF GRAVITY.
Johnx64
[H]F Junkie
- Joined
- Apr 22, 2002
- Messages
- 9,326
So a bullet is traveling sideways. It's forcing itself through the air. Gravity is pulling down on it. The bottom half wont have more pressure even though it's being pulled down creating more pressure on the bottom half. Let me make another illustration real quick
Damn typo in the picture
Damn typo in the picture
S0m30n3 said:So a bullet is traveling sideways. It's forcing itself through the air. Gravity is pulling down on it. The bottom half wont have more pressure even though it's being pulled down creating more pressure on the bottom half. Let me make another illustration real quick
Damn typo in the picture
No it wont. All it would do is pull the bullet down. The force of the bullet wont overcome the force of gravity. and the bullet is uniform in shape, so the pressure is equal on all sides. the gravity pulling down won't cause any new pressure. the reason bullets fly is because the force is so great (out of the gun) that the bullet is thrown out of the gun, faster then the speed it would take gravity to pull it down. It's the same concept as throwing a baseball, it also goes horizontaly, doesn't mean that gravity is creating pressure on it or something.
I will reiterate
WE HAVE NOT YET CREATED SOMETHING THAT CAN CHANGE THE LAWS OF GRAVITY OR PHYSICS
All that gravity does with anything, bullets, planes, gliders, baseballs, is pull the objexts to the ground, nothing more, nothing less.
I think S0m30n3 needs to figure out what a "vector" is before this conversation will make any sense.
Another minor point, gravity doesn't only affect the bottom of an object, it affectst the whole thing. There's no difference in gravitational force on the top of the bullet versus the bottom. That's one reason, among many, that your "pressure differential causes lift" idea doesn't work. Airplanes stay in the air because their wings are not symmetrical and an upward force is created. Bullets are symmetrical and create no upward force.
This might help reconcile your mental pictures of how this works: You know it doesn't take long for a bullet to fall to the ground if you drop it. You think a bullet that is fired goes a long way, so it cannot fall as fast. However, it moves laterally REALLY DAMN FAST, so it can hit whatever it was fired at before it hits the ground. Hopefully that helps you process this idea a little easier.
Another minor point, gravity doesn't only affect the bottom of an object, it affectst the whole thing. There's no difference in gravitational force on the top of the bullet versus the bottom. That's one reason, among many, that your "pressure differential causes lift" idea doesn't work. Airplanes stay in the air because their wings are not symmetrical and an upward force is created. Bullets are symmetrical and create no upward force.
This might help reconcile your mental pictures of how this works: You know it doesn't take long for a bullet to fall to the ground if you drop it. You think a bullet that is fired goes a long way, so it cannot fall as fast. However, it moves laterally REALLY DAMN FAST, so it can hit whatever it was fired at before it hits the ground. Hopefully that helps you process this idea a little easier.
i could really chime in on this, but i can't remember any of the math behind it, just food for thought about the bullet though, my 25-20 fires a slug at around 3200 Feet Per Sec, gravity's pull is 9.8 Meters per sec squared, there is a ton more force behind the bullet, and as the force is lost due to air resistance the rate of decent will increase. The bullet, (the entire thing) will be affected by gravity, not just the bottom. When in high school and i studied pyhsics, we neglected air resistance cause it just messes with ya a lot, lol
Oh, and about the "WE HAVE NOT YET CREATED SOMETHING THAT CAN CHANGE THE LAWS OF GRAVITY OR PHYSICS"
true, well that we know of
Oh, and about the "WE HAVE NOT YET CREATED SOMETHING THAT CAN CHANGE THE LAWS OF GRAVITY OR PHYSICS"
true, well that we know of
k1pp3r said:
Actually, you got one thing wrong. The rate of descent will not change as the bullet slows down due to air resistance. It would increase relative to the horizontal velocity, but it'll continue to increase at 9.8 m/s^2, same as it always would.
But yeah, use that 3200 feet per second figure. Assume it stays vaguely constant. That bullet is going to go an awfully long way before it hits the ground.
Kadarom Douhrek
2[H]4U
- Joined
- Apr 14, 2001
- Messages
- 2,876
S0m30n3 is partially correct, but is ignoring some things incorrectly applying others.
There will be greater air pressure on the underside of the bullet.
The bullets forward air speed will create a change in air pressure around the bullet.
As per fluid dynamics and the bullets symetrical shape the pressure change will be identical on all sides.
However as gravity accelerates the bullet towards Earth there will be airflow accross the bullet creating a higher pressure area under the bullet and a lower pressure area over it.
This is called air resistance and the other bullet, assuming it was dropped horizontally, will experience the same verticall air resistance, or increased pressure on the underside.
Both will still hit at the same time.
Well, assuming a whole list of other realworld variables such as manufacturing irregularities and bullet deformation.
There will be greater air pressure on the underside of the bullet.
The bullets forward air speed will create a change in air pressure around the bullet.
As per fluid dynamics and the bullets symetrical shape the pressure change will be identical on all sides.
However as gravity accelerates the bullet towards Earth there will be airflow accross the bullet creating a higher pressure area under the bullet and a lower pressure area over it.
This is called air resistance and the other bullet, assuming it was dropped horizontally, will experience the same verticall air resistance, or increased pressure on the underside.
Both will still hit at the same time.
Well, assuming a whole list of other realworld variables such as manufacturing irregularities and bullet deformation.
Kadarom Douhrek said:S0m30n3 is partially correct, but is ignoring some things incorrectly applying others.
There will be greater air pressure on the underside of the bullet.
The bullets forward air speed will create a change in air pressure around the bullet.
As per fluid dynamics and the bullets symetrical shape the pressure change will be identical on all sides.
However as gravity accelerates the bullet towards Earth there will be airflow accross the bullet creating a higher pressure area under the bullet and a lower pressure area over it.
This is called air resistance and the other bullet, assuming it was dropped horizontally, will experience the same verticall air resistance, or increased pressure on the underside.
Both will still hit at the same time.
Well, assuming a whole list of other realworld variables such as manufacturing irregularities and bullet deformation.
QFT
The reason you wont have greater pressure on the bottome of the bullet, is because the bullet is in an open area
heres a picture:
Basically, the air is allowed to escape to the sides, so no pressure is created
however, if the bullet was shot in in an area like this:
then prssure would be created, but the box would have to travel with the bullet, so air cannot escape from the front or back
(click the pics so you can see all the writing)
edit: also, the pressure (when in the open) will be uniform all around the bullet in free flight, because:
A) The bullet is uniform in shape (it doesnt matter if it is flying the the ground or not, it is still flying straight, air passes over it uniformly)
and B) Becuase the bullet spins while flying
heres a picture:
Basically, the air is allowed to escape to the sides, so no pressure is created
however, if the bullet was shot in in an area like this:
then prssure would be created, but the box would have to travel with the bullet, so air cannot escape from the front or back
(click the pics so you can see all the writing)
edit: also, the pressure (when in the open) will be uniform all around the bullet in free flight, because:
A) The bullet is uniform in shape (it doesnt matter if it is flying the the ground or not, it is still flying straight, air passes over it uniformly)
and B) Becuase the bullet spins while flying
The heavier the object the faster it falls to the earth theoretically speaking, as stated by the law of universal gravitation and negating air resistance. In reality, the difference in speed is negligible.magoo said:Basic Physics, Galileo tested this at Pizza. F=ma. force=massxacceleration force is the simple force of gravity,which on any object is the same. allowing for resistance ALL things fall at the same speed. That would be 9.8 meters squared, the force of gravity,that is. I think my daughter learned this this year in 6th grade.
to the guy that thought bullets floated(or stayed int he air longer). there is no pressure diff, if there was, like that guy said it woulde be relieved by the air going to the sides, so it would effect it (if at all') by like the smallest increment. but u see, if ur little air pressure thing worked, then wouldnt u get the same effect droping a bullet? therefore, they would still drop at the same time. also even if the bullet had some feature lol, to put more pressure downward, its spinning, so it would put the same force all around. also , i think the only reason that u think bullets that have been shot stay up longer, is because u dont realize that the bullet gets to its desination so fast, it has little time to drop, so it looks like it stayed "floating" in the air longer
They will both face the same amount of vertical air resistance--bipolar
They will both face the same amount of vertical air resistance--bipolar
sry lol. i just made a huge virtual chalk board thing for myself, and realized that guy was right lol, the bullet wil stay afloat for the smallest increment longer, assuming u drop them as ive shown.i need a picture showing thing thatls work w/ any size u cantr really read this....
http://i4.photobucket.com/albums/y135/arekey29/untitled.bmp
u cantr really read this.... http://i4.photobucket.com/albums/y135/arekey29/untitled.bmp
Neurofreeze
2[H]4U
- Joined
- Jan 11, 2002
- Messages
- 2,523
Wow, way off topic.
Now back on topic:
Both visuals and physics are tools for immersion, however neither are strictly needed for the most important aspect of the game. No, it's not gameplay. That's just an amorphous phrase used to describe anything from what a game lacks to at what it excels. The most important aspect is fun. Is the game fun?
The focus on physics engines are to:
1) Compliment the graphics engine
2) Create fun reactions, not necessarily realistic ones
Yes, there's obvious room for improvement, but the graphics revolution came with an explosion in video card horsepower in a very short period of time. Unless a similar explosion in CPU horsepower comes about I don't see physics engines undergoing a similar revolution (although with multicore systems you never know). Bouncing miltary vehicles and literally rag doll physics are a problem though.... Give it a few generations.
Now back on topic:
Both visuals and physics are tools for immersion, however neither are strictly needed for the most important aspect of the game. No, it's not gameplay. That's just an amorphous phrase used to describe anything from what a game lacks to at what it excels. The most important aspect is fun. Is the game fun?
The focus on physics engines are to:
1) Compliment the graphics engine
2) Create fun reactions, not necessarily realistic ones
Yes, there's obvious room for improvement, but the graphics revolution came with an explosion in video card horsepower in a very short period of time. Unless a similar explosion in CPU horsepower comes about I don't see physics engines undergoing a similar revolution (although with multicore systems you never know). Bouncing miltary vehicles and literally rag doll physics are a problem though.... Give it a few generations.
Johnx64
[H]F Junkie
- Joined
- Apr 22, 2002
- Messages
- 9,326
ooo I get it. Sorry I wasted some of your time hehehe.
One thing which annoys me far more than this whole rag-doll stuff is with more basic things like walking, running, etc.
Whenever a character is walking, unless the floor is really slippery, its foot should not shift position. Everyday experiences will tell you that if you put your foot down on the ground, and this foot suddenly slides forward a number of centimeters, you risk losing your balance. What one can observe in games, however, is that characters apparently do not walk at all, but merely float a couple of millimeters above the ground, and thus can slide forward/backward with no balancing issues at all.
Observe characters walking against a door, before readjusting to finally open it.
Another point, which also plays a role in rag-doll physics, is the apparent absence of mass, such as when moving one's arm, head or other appendage, or when an object falls (collapsing structures, e.g., houses). Objects have mass, which equals inertia, which equals a certain amount of kinetic energy when moving and hence do require a certain distance to come to a full stop, or when slamming into something, this energy has to affect both the object and the surface/object it hits.
Paper, indeed
Whenever a character is walking, unless the floor is really slippery, its foot should not shift position. Everyday experiences will tell you that if you put your foot down on the ground, and this foot suddenly slides forward a number of centimeters, you risk losing your balance. What one can observe in games, however, is that characters apparently do not walk at all, but merely float a couple of millimeters above the ground, and thus can slide forward/backward with no balancing issues at all.
Observe characters walking against a door, before readjusting to finally open it.
Another point, which also plays a role in rag-doll physics, is the apparent absence of mass, such as when moving one's arm, head or other appendage, or when an object falls (collapsing structures, e.g., houses). Objects have mass, which equals inertia, which equals a certain amount of kinetic energy when moving and hence do require a certain distance to come to a full stop, or when slamming into something, this energy has to affect both the object and the surface/object it hits.
Paper, indeed
Elledan said:One thing which annoys me far more than this whole rag-doll stuff is with more basic things like walking, running, etc.
Whenever a character is walking, unless the floor is really slippery, its foot should not shift position. Everyday experiences will tell you that if you put your foot down on the ground, and this foot suddenly slides forward a number of centimeters, you risk losing your balance. What one can observe in games, however, is that characters apparently do not walk at all, but merely float a couple of millimeters above the ground, and thus can slide forward/backward with no balancing issues at all.
Observe characters walking against a door, before readjusting to finally open it.
Another point, which also plays a role in rag-doll physics, is the apparent absence of mass, such as when moving one's arm, head or other appendage, or when an object falls (collapsing structures, e.g., houses). Objects have mass, which equals inertia, which equals a certain amount of kinetic energy when moving and hence do require a certain distance to come to a full stop, or when slamming into something, this energy has to affect both the object and the surface/object it hits.
Paper, indeed
Even better, try playing splinter cell and watch them walk up or down stairs.
Newer game engines have alevated this problem a bit atleast. Now the feet seems to move independent from the body. I tried stopping a guy in Doom3 midstride while he was walking up a small flight of stairs and his feet actually matched the stairs (One foot on the top stair, the other on the lower one). Simple, but that was only the second time i've seen that happen in a game (The first was MechWarrior 3)
On the door thing, try playing SWAT4. The developers have that little issue covered atleast
I don't get your point on the ragdoll effect tho. I've thrown maxpayne2 bad guys against various objects and they seem to transfer the kinetic energy to other objects just fine. Same with PainKiller
I don't necessarily mean it in regard to characters. Say, a building collapses, and large fragments of the walls fall down on the ground below. I haven't seen a single game in which it actually looks like pieces of a wall hitting tarmac, concrete, soft ground or whatever.Sly said:I don't get your point on the ragdoll effect tho. I've thrown maxpayne2 bad guys against various objects and they seem to transfer the kinetic energy to other objects just fine. Same with PainKiller
<and others>bipolar said:Well, the problem is I can't imagine any material the size of a parachute weighing 90 tons that would unfurl in the same manner. For the sake of arguement, let's say you're somehow magically teleported 5000 feet up with a parachute made of concrete that is formed to be exactly the same shape as a silk parachute when fully extended. Then yes, it would work equally as well. Landing would be a bitch though -- better cover your head
Sorry for brining this up again, but I simply have to respond.
All this takes place on this planet, with an atmosphere, right above your house at sunny weather conditions 24°C, no noticable winds, perfect weather to be outside.
Imagine having 2 baloons, one is filled with helium, the other with water, both have a diameter of 30cm.
Will both baloons behave the same way? Will both drop to the ground at the same speed when let go at .. 100m height?
--------
Imagine two parachutes, both of the same size and shape, made of the same material. One carries a human, the other a replica of that human made of pure steel.
Will both parachutes reach the ground at the same time when droped from the plane at .. 5000m height?
--------
What about putting two barrels onto some quicksand - one emtpy, the other filled with lead - will both sink at the same rate?
--------
I realy was amazed when reading this thread, so many false information on even the easiest things. I understand the confusion about the bullet drop experiment, but please, two object of the same size/shape but different weight accellerate at the same speed when droped here on earth? Or into the ocean?
Come on...
Yes, they will, the parachute example is flawed, because the same size parachute would not function properly for two different weights and then you have to bring into play terminal velocity etc, which is a function of drag, not weight.Sneaky said:
Youre right, both balloons will not behave the same, but, they will have the same effects as gravity, again, its a different argument.
I cant comment on the quicksand example, because ive never done a non-newtonian fluids course, i dare say teh heavy one would actually sink slower, since the viscosity of something like quicksand is inverse to the force applied, although i may be wrong on that. However the two barrels dropped into water/air would both sink at the same rate yes.
forcemac101
[H]ard|Gawd
- Joined
- Feb 28, 2001
- Messages
- 2,031
Now for a physics lesson boys and girls....this will blow every 12 year old's mind on these boards....
You are standing in field and you have a bullet in your hand, and you have an identical bullet in a gun in your other hand. If you were to fire the gun perfectly level such that bullet flies perfect level, and at the same time drop the bullet from your other hand from the same height at which you had the gun, both bullets would hit the ground at the exact same time (ignoring wind induced irregularites that might cause some lift or vertical vector).
Hows that for a mind job. Look it up, its a physics 101 example. The reason is that both bullets have the same vertical acceleration working on them...gravity. The horizontal speed at which the one bullet was fired has absolutely no effect on how fast it falls. It will hit the earth exactly the same time as the one dropped by your other hand...except that will be x amount of feet from you given time it takes to drop the the earth multiplied by the muzzle velocity.
12 year olds heads exploding now....haha
You are standing in field and you have a bullet in your hand, and you have an identical bullet in a gun in your other hand. If you were to fire the gun perfectly level such that bullet flies perfect level, and at the same time drop the bullet from your other hand from the same height at which you had the gun, both bullets would hit the ground at the exact same time (ignoring wind induced irregularites that might cause some lift or vertical vector).
Hows that for a mind job. Look it up, its a physics 101 example. The reason is that both bullets have the same vertical acceleration working on them...gravity. The horizontal speed at which the one bullet was fired has absolutely no effect on how fast it falls. It will hit the earth exactly the same time as the one dropped by your other hand...except that will be x amount of feet from you given time it takes to drop the the earth multiplied by the muzzle velocity.
12 year olds heads exploding now....haha
Sneaky said:
Hmm... Never considered this before but provided they were dropped in a vaccum, i'd surmise that they will still hit the ground at the same time. Helium is just a matter of buoyancy in a heavier atmosphere, if there's no atmosphere (like a vaccum) it's still just deadweight.
Herulach said:
No, the parachute example is not flawed.
Instead of a parachute you could as well take an object with exactly the shape of said parachutes+person attached.
Please explain how the balloons are different - both are objects with different weight, same shape and form - they fit perfectly into what we are argueing - how items droped in x height into our atmosphere behave.
I am not argueing that those object will behave the same when drop in a vacuum, S0m30n3 wasn't either. But people state they will accelerate with the same speed when droped in an atmosphere, which, imho, is BS.
pr0pensity
[H]ard|Gawd
- Joined
- Sep 2, 2003
- Messages
- 1,738
Air would push the helium out of the way as it is heavier.
The man would have a predictably lower terminal velocity. This is an effect of air friction opposing gravity and not a property of gravity itself.
Same as above.
In most cases, most objects will. A wooden plank dropped from a building will hit the ground at about the same time as a car dropped from the same height. Not exactly the same, but for all practical purposes, air resistance has no effect on the objects.
Extreme cases such as a feather to a steel dumbell are impertinent.
I'm certain everyone in this thread knows that a feather falls slowly and why.
Heavier objects are affected more by gravity, yes, but this is exactly countered by their inertia.
you know, the backup plan for those who did smoke weed n got drunk in highschool. lolUSMC2Hard4U said:Am i the only one in life that smoked weed and got drunk in school? Physics? They wouldnt even let me take that class because I failed Algebra 2....
This thread hurt my brain. Fuckin smart people.
pr0pensity
[H]ard|Gawd
- Joined
- Sep 2, 2003
- Messages
- 1,738
bipolar said:
1. If the doors of the truck are closed, then there is no way for the energy to be displaced. The canaries' wings are pushing against air, which is pushing against the truck, so it weighs the same all the time.
If the doors are open the moving air could be pushed outside, converting vertical energy into lateral and taking some pressure off the floor of the truck.
2. Air resistance would be pretty significant with that much energy involved on such a small object. But ignoring air, it would land at just the same speed as it started. There is no gain or loss of evergy.