Is there such thing as air resistance without friction?
820353
You've presented a paradox:  How can you have air friction in a frictionless world?  \n\nAir resistance and air friction are two terms for the same phenomena.
900569
No, air pressure is applied in all directions. Down, as well as up. The downward air pressure is negated by the equal upwards pressure.
808868
Sandpaper rough    course  harsh abrasive different guages of courseness,  Air would not have a problem passing over them however could take longer to travel over sandpaper,\ncling film smooth in comparison. and air would travel unhindered.
868820
the answer above is wrong to a degree - in your example i would have to imagine falling through a vacuum therefore if he didn't touch the sides his momentum would carry him to the other side and then back again over and over\n\nthe answer above ( 1st ) assumes air resistance would slow him down but he would go back and forth for a long time before stopping\n\nthe gravity would decrease on the way down and increase on the way up but not in the way you think what would happen is that the gravity would be pulling from the side more and more the deeper you got ( so the effect is only virtual) you would always be in a 1g field it is just the direction(s) of the pull that would change\nthe direction of the most mass at any one time would appear to be down and at the center all pulls ( 360 degrees ) would seem to cancel one another ( but they would still be there )
136353
If you consider a model in which both surfaces which cause friction have crusts and troughs, and their interlocking causes the frictional resistance, then it is explained as follows.\n\nThe lubricant molecules fill up the troughs in both surfaces and make them more or less even, and hence there is less interlocking among the two surfaces, and so less friction.
683735
The path of least resistance?
496203
without friction, the car will not move when the wheel is turning. without friction, the wheel will not stop when u step on the brake. even if it stops, the car will not stop. without friction, u can't hold anything in your hand. u cannot stand upright. your glasses will not stay on your face. u will slide off your chair. everything would slide around.\n\nwithout friction, less energy is loss as heat and noise. less energy would be needed to power an engine. tire would not wear out. thing in motion would move longer.\n\nu get the idea
133048
Hello, \n\nThis problem is a bit more involved than you might initially think. There are 4 major considerations you must take into account. First, the acceleration is dependant on the angle of the hill at any given time. Therefore, acceleration is NOT constant, rather fluctuating with the incline. Second, the wind resistance is NOT constant by any means. It increases exponentially with the speed of the sled. Third, the force of the kinetic friction is not constant either. While the coefficient of friction does increase somewhat with speed (you could use an average for this), you cannot neglect the increase in friction when the sled goes around a corner. As you know, the friction is based on the normal force of the sled. At 90mph, the centripetal acceleration around a curve is V^2/r (V=velocity, r is radius of corner) which becomes quite considerable, even though steel on ice only has a kinetic coefficient between .01 - .05. \n\nNow that I have bored you out of your mind, the full equation would look something like this (I’m writing everything longhand so you know what I’m talking about)\nSum of the forces = mass x gravity x sin(angle of hill) – [(coefficient of friction) x mass x gravity x cos(angle of hill) – mass x velocity ^2 / radius of curve] – (Force of air drag)\n\nNotice the term included to account for curves: – mass x velocity ^2 / radius of curve\nDrops to zero when they are going in a straight line (r = infinity). \n\nTo find your acceleration (at a specific point in time), you simply divide everything by the mass of the sled and there you go!\n\nPS. don't take physics advice from dental students ;P
481512
I believe a cylindrical kite can fly. If you think about it there is space for the air to move through and yet there is a structure to create resistance. The air would move the the open cylindrical design, but at the same time, the walls of it would allow resistance for the air to hit and allow resistance in order to keep it in the air......that's what i think, i dont know about the no wind part though.
788371
Air has pressure, much like any gas.  By using this pressure it fills in cracks and crevices.
26736
look up stuff like static friction, and your coefficient of friction...
662183
no.  air friction will limit it's terminal velocity.  It'll still hurt, and possibly kill if it strikes someone
276284
The answer to that question depends on many factors.  However the military practices this phenom daily.  each element has a combustion point.  Freashman Physics does not delve into the properties of air friction as it relates to projectile motion.   \n\nnow for the basic answer.  I will leave the details for you to research.  Understanding science is much superior to being given a fish.\n\nTracer rounds in in military machine gunds are composed of standard bullets whose tips are coated with Phosphorous.  the are inserted every fourth round but when fired the velocity of round, its surface area, and the friction due to  air cause a net resultant heat that surpasses the combustion pint of Phosphorus.  My spelling sucks but hopefully my theory is sound.
561115
Question -   Please explain how molecules in the air cause air\nresistance. Why air resistance is larger when a car a travelling faster?\n---------------------\nSharazaad,\n\nEven though you cannot see them, air molecules (a mixture of gases, mainly nitrogen and oxygen) are \njust like all other molecules inasmuch as they have mass and occupy space. Anything moving through \nair must push the molecules out of the way.\n\nThe faster the object moves, the faster the air molecules are encountered and the greater are the \nnumber to be pushed aside. This requires a larger force that necessary when the object is moving \nslowly. Consider swimming: The faster you swim, the harder it is to push the water molecules out \nof the way.\n\nStreamlining a car is a way of making it slip through the air more easily. Cars with narrow or \nwedge-shaped front ends and smooth, gentle curves allow it to slip through the air more easily \nthan bulky things like large trucks with large, boxy, flat front ends. Even something so simple \nas keeping a car clean and polished will help it slip through the air more easily.\n\nRegards,\nProfHoff 869\n=====================================================\nSharazaad,\n\n\nMolecules in the air have mass.  Even though they are invisible, they are\nstill there, and they still have to be pushed out of the way for a car to\noccupy the space that the air is in.  This now should make sense WHY air\nresistance even exists.\n\nNOW.  Why do greater speeds cause there to be an even greater air\nresistance.  It is true that there is barely any appreciable air resistance\nto a car going 10 MPH versus 60 MPH.  But at 60 MPH, even though there is\nthe same amount of air, the resistance is much greater because the car needs\nto move the air out of the way MUCH MUCH QUICKER.  I do not know if you can\nreally speak about viscosity of air (non - liquid).  But air really does\nbehave like a liquid when it comes to resistance.  HOW?  The air that is\nexisting on or above the sidewalk WILL ALSO RESIST the air molecule that is\nbeing struck by your car and pushed to the side.  SO, this is why at higher\nspeeds you will have a much greater resistance because you are FORCING THE\nAIR to move not at 10 MPH but NEEDING IT to move out of the way at 60 MPH.\n\nYou could say that the relationship between air resistance (r) and velocity\n(v) is proportional.  However, I think I read somewhere that resistance (r)\nis ~ velocity (v)^1.5\n\nPlease do not quote me on that ... but I am pretty certain I read it in an\nMath book for Engineers.  So there may be some credence to it.\n\nHope this helps.\nDarin Wagner\n=====================================================\nAir resistance is caused by the car banging into air molecules and\nincreasing their momentum in the direction the car is going.  Since the car\nexerts a forward directed force on the molecule, by Newton's 2nd law (for\nevery action there is an equal and opposite reaction) the molecule exerts a\nforce on the car in the backward direction, tending to slow the car.\n\n\nOf course, a molecule has so little mass, it exerts an extremely tiny force\non the car.  However, there are so many molecules that the cumulative effect\ncan be large.  You might also imagine what would happen if molecules were as\nlarge as bowling balls!  I think you can picture how the forces could be\nvery large.\n\n\nIncidentally, the molecules are moving at speeds much faster than the car is\ngoing and in random directions.  So some hit the car from the rear and speed\nit up a little (very little).  However, one coming from the front slows the\ncar down by a larger amount because the car's speed is added to the\nmolecule's speed for a molecule coming from the front and subtracted from\nthe molecule's speed for one coming from the rear.\n\n\nBest, Dick Plano, Professor of Physics emeritus, Rutgers University\n=====================================================\nHi Sharazaad,\n\nGood question,
165147
When a bag of nails reaches its terminal speed, the force of the air is exactly equal to the force exerted downward, so the bag no longer accelerates.  Therefore, the amount of air resistance is 100 N.
950717
in order for perpetual motion to occur, both surfaces have to be frictionless, and there can't be any air density.  Eventually, the ball in your question will stop as a result of friction from the table and air resistance.
814087
It would actually work better if there were no outside air.  There would be no air resistance to deflect it or slow it down.