What is Air drag: Definition and 58 Discussions

In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, drag force depends on velocity.Drag force is proportional to the velocity for a laminar flow and the squared velocity for a turbulent flow. Even though the ultimate cause of a drag is viscous friction, the turbulent drag is independent of viscosity.Drag forces always decrease fluid velocity relative to the solid object in the fluid's path.

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  1. S

    Air Friction energy loss on a trampoline

    Consider a 5 m diamter trampoline. It has an area of not quite 20 m2 If a jumper sinks 1 meter into the mat at center, the volume of the displacement cone is 6.5 m3 (1/3 base of cone times height) Because air as to move in over the top, as well as get out from under, the air moved per jump...
  2. Argonaut

    Maximizing Range/Time in Air of an Airplane: Solving with Calculus

    Is my solution correct? (I only have answers to odd-numbered exercises.) Is it a good solution or have I overcomplicated things? (a) The forward force provided by the engine balances the air resistance force, so ##F_{engine}=F_{air} = \alpha v^2 + \beta /v{^2}##. Let ##W_{engine}## be the...
  3. A

    I Drag equation - relative flow velocity

    Hello! I have a question about aerodynamic drag. It sounds simple but when trying to understand why the relative velocity can be used in calculations I have some trouble. The formula is 0.5*rho*u2*cd*A where u is the relative velocity between the object and the fluid. The cd value depends on the...
  4. T

    Projectile Motion with Air Drag

    Tell me now if this question is posted in the wrong place. This isn't a homework problem per se, it's just a question I need answered and I'm not sure how to answer it. If there is any information missing, chances are I know it and forgot to post it, so please ask if something is missing. I...
  5. M

    B Is there an analytical solution to this equation?

    So I've derived the rocket equation in empty space and with constant gravity. Now I am interested in adding air resistance. I'm aware that there are 2 different models as if 0<Re<1 then F_drag=k*v and if 1000<Re<30000 then F_drag=1/2*A*rho*CD*v^2. And for my purpose the second model is most...
  6. Dr. Courtney

    How Can Doppler Radar Improve Drag Coefficient Measurements in Physics Labs?

    https://aapt.scitation.org/doi/10.1119/1.5064562 The availability of inexpensive Doppler radar has made it practical to accurately measure drag coefficients in undergrad physics labs.ABSTRACT Undergraduate lab design balances several factors: 1) simple experiments connected with learning...
  7. babaliaris

    Air drag force: Why heavy objects accelerate faster?

    I've done the math but because i can't find this answer anywhere in the book which I'm reading and on the web, I would like to be sure if my calculations are correct. I know that if two objects (starting at the same time) are free falling without a drag force being applied to them, the...
  8. M

    Dimensions of Air Drag Constants and Terminal Speed Equation

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  9. A

    Drag Force: Mass & Why It Doesn't Affect Object

    Why drag force doesn't Depend on the mass of the Object?
  10. C

    Differential Equation for Projectile Motion with Air Drag

    Hi! I was wondering how I could come up with a differential equation for projectile motion on a 2D plane when air resistance is not negligible. I'm trying to guess the position of a projected ball at a certain time period by approximating the coordinates using the Euler's method. Here, I would...
  11. N

    What takes longer? With airdrag or without?

    Heey all, Do you think it will take longer for an object shot from the ground vertically to reach to ground again with air resistance or without? Keep in mind, no air drag means it will go higher, but it won't be slower down on the way back.
  12. J

    Finding Impact Depth: Most Realistic Way Possible

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  13. R

    If air drag is a factor, how will it affect a projectile?

    If air drag is a factor, how will it affect a projectile’s trajectory qualitatively? Its velocity? Its acceleration?
  14. victorhugo

    What do we know about the formula for air drag force?

    Is it the typical "get some results and stack the maths together and chuck in some constants to make it fit to get some approximation" or do we understand the rules behind it to derive the formula, such as how the molecules repel each other and how energy is transferred depending on temperature...
  15. E

    How do I calculate the work due to air drag when throwing a ball in the air?

    Homework Statement There isn't really a "problem statement", but more so a conceptual prompt. Say you throw a ball in the air with some velocity V. The work done due to gravity and drag is Mgh + Fdragd. What I don't know how to do (and there is no additional information, the prompt is very...
  16. 4

    How to Reduce Air Drag for Vehicles?

    Hello everyone! I was thinking about how to reduce air drag for a vehicle so that one gets better mileage. Here is the definition of the problem: A moving car faces air drag especially at high speed. The resistance of the air layers would try to slow down the car. In order to maintain the same...
  17. M

    Calculating velocity of a bullet with quadratic air drag

    So this problem was a 2 part question. The first part goes as such. 1. A gun is fired straight up. Assuming that the air drag on the bullet varies quadratically with speed, show that the speed varies with height according to the equations: v2 = Ae-2kx - (g/k) (upward motion) v2 = (g/k) -...
  18. AdityaDev

    Air Drag & No Drag on a Ball Projected Vertically

    < Moderator Note -- thread moved from General Physics to Homework Help forum > If a ball is projected vertically upwards say with a velocity V. Case 1: Without air drag Case 2: With air drag What will be the difference in v-t graphs and the motion of the ball Air drag D=bv (b is a constant,v...
  19. J

    Need help with deriving air drag equation

    △Work = △KE + △PE Work = Force x Distance W=F△x Pressure = Force/Area W=PA△x Volume=Area x length W=PV Work = Pressure x Volume KE=(1/2)mv^2 Density = mass/volume mass = density x volume m=DV KE=(1/2)DVv^2 (work done by air pressure?) PE=mgy PE=DVgy (work done by gravity and air pressure??)...
  20. U

    Equation for upward motion of the particle with air drag

    Homework Statement A particle of mass m is thrown upward with velocity v and there is retarding air resistance proportional to the square of the velocity with proportionality constant k. if the particle attains a maximum height after time t, and g is the gravitational acceleration, what is...
  21. D

    (simplified?) Air drag force question.

    My issue/knowledge Hello all, I think this is my first time posting a question here (I have read the guidelines). This problem is not in my textbook or notes, and I'm not sure how to go about it. Online all I can find about air drag equations requires knowing variables which I'm not given here...
  22. N

    Bullet Range Neglecting Air Drag

    Hello All, Homework Statement I was at the firing range the other day when the gun instructor mentioned that the bullet of a AR-15 rifle can travel 5 - 6 miles depending on the angle of the gun when the bullet leaves the muzzle. I wanted to confirm this for myself so, I tried to find the...
  23. V

    How much is the ideal rocket equation affected by air drag?

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  24. M

    Finding Velocity with Air Drag

    Homework Statement I am trying to find the velocity of a car as it is going down hill. I have the final velocity which is 11.2 m/s and the initial velocity which is 2.23m/s. I have to include Air drag to get my velocity. I also know that there was 21,456 J of energy lost from up the hill to...
  25. ferret_guy

    How to calculate trajectory of an object with air drag

    I am trying to predict the flight of an object with a parabolic trajectory including drag due to air resistance how do I do this? the wiki page was not clear its my understanding its relative to the square of the speed.
  26. P

    Exploring physical concepts (buoyancy, air drag) but afraid of the math.

    Hello! I have just rediscovered this place since a few years back when I first signed up. This will be my first post, so forgive me if it is a bit long. I have been thinking about this for a while. So I have been thinking about buoyancy. I have learned that the buoyancy force is caused by...
  27. E

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    Homework Statement On September 8, 2004, the Genesis spacecraft crashed in the Utah desert because its parachute did not open. The 210-kg capsule hit the ground at 311 km/h and penetrated the soil to a depth of 81.0cm . Assuming it to be constant, what was its acceleration (in m/s2 )...
  28. S

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  29. S

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  30. F

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    We have \dfrac{d}{dt}\left(\dfrac{\partial \mathcal L}{\partial \dot{q}_j}\right)-\dfrac{\partial \mathcal L}{\partial q_j}=-\dfrac{\partial \mathcal F}{\partial \dot{q}_j}. If the force of friction is F=-kv^2 how do you go about calculating \mathcal F My idea is as follows F=-kv^2...
  31. C

    Calculate Velocity of Skydiver: Mass M, Air Drag Coefficient D

    Calculate velocity of the skydiver of mass M= 80kg as a function of time. The air drag coefficient D= 100g/m = 0.1kg/m. Assume that the skydiver has v=o at t=0. In my book high speed air drag is f=Dv^2. I found Vt= 88.5 m/s with Sqrt(mg/D). BUT this is not the V they are asking for :(...
  32. U

    Air drag and acceleration (not gravity)

    In physics class we made a rocket and test fired it. Now we are given the thrust and we found out the max height of the rocket and the time of flight. Max Height = 76m Time of thrust/ upward acceleration = .8s Time of flight with only gravity acting until velocity is 0 . = 4.96s (not...
  33. U

    Air drag and acceleration (not gravity)

    In physics class we made a rocket and test fired it. Now we are given the thrust and we found out the max height of the rocket and the time of flight. Max Height = 76m Time of thrust/ upward acceleration = .8s Time of flight with only gravity acting until velocity is 0 . = 4.96s (not...
  34. M

    Show that air drag varies quadratically with speed

    Homework Statement A gun is fired straight up. Assuming that the air drag on the bullet varies quadratically with speed. Show that speed varies with height according to the equations v^2 = Ae^(-2kx) - g/k (upward motion) V^2 = g/k - Be^(2kx) (downward motion) in which A and B are...
  35. I

    If raindrops fell with no air drag how long would it take?

    Homework Statement If there were no air drag, how fast would drops fall from a cloud 1.6 kilometer above the Earth's surface? Homework Equations am i heading in the right direction if not what am i doing wrong? The Attempt at a Solution i tried converting to m first then i...
  36. D

    A baseball's movement when considering air drag

    Homework Statement A baseball, with mass m = 0.145 kg, is thrown directly upward from z(0) = 0 m, with initial speed v(0) = 45 m/s. The air drag on the ball is given by Cv2, C = 0.0013 Ns2/m2. Set up a diff. eq. for the ball's movement and solve it for both v(t) and z(t). m = 0.145 kg C =...
  37. C

    Air drag on a wire moving lengthways

    Can anyone help me work out the air resistence on a wire as it moves along its length? I think it would only experience skin friction if it moved like this and the wire was smooth, so does anyone know how to calculate this? I am having difficulty looking it up.
  38. D

    Fall with Air Drag - Which Value for Velocity to Use?

    Homework Statement I want to numerically simulate a fall with air drag. In class, we used these equations to produce a table simulating free fall (using a ti calculator): dt=0.1s a=9.81m/s² tn+1=tn+dt vn+1=vn+a*dt xn+1=xn+vn*dt When I compared that system with the curve produced by the...
  39. E

    Calculating Displacement with Air Drag: A Differential Equation Approach

    This is not a homework problem, just an idea I had. If we have a sphere which is being accelerated in space by a force \vec{F} and we take the drag into account, what would the displacement be after t seconds? If the drag force is \vec{D}=-c_1v-c_2v^2, then the acceleration would be...
  40. J

    How does air resistance change with acceleration?

    Hello and thanks to all who read this. Recently I've just been messing around with air drag equations, trying to extend applied maths problems to include air drag. And I've hit a road block, at least with regards to my knowledge anyway. I've been using the F_drag = 1/2 P (mass density of...
  41. A

    Conservation of energy problem (projectile with air drag)

    Homework Statement A stone with weight w is thrown vertically upward into the air from ground level with initial speed v0. If a constant force f due to air drag acts on the stone throughout its flight, (a) show that the maximum height reached by the stone is h = \frac{v_0^2}{2g(1+f/w)}...
  42. Z

    The air drag and magnus pass spin axis?

    The air drag and magnus pass through spin axis? A ball is flying in the air, and it has spin on y axis, show below. F1 is the air drag force. F2 is the magnus force. My question is: the air drag and the magnus force is pass through the spin axis? Or, the ball will change the torque...
  43. V

    Air Drag Formula: Solving Maik's Rocket Project Challenge

    Hello, I'm working on a project about solid fuel rockets and since these are moving through the atmosphere, they experience Air-drag. I'm trying to set up a formula to exactly calculate the height a rocket will achieve. So without the use of any model. The problem I ran into is that I can't...
  44. V

    Solving Air Drag Equation: A Guide for Beginners

    Hey, I'm having some problems trying to solve the equation for air drag. I'm currently doing a project about solidfuel rockets and air drag is a big deal =) I used this equation for dragforce (Fd) Fd(t)= -0,5 * p * A * Cd (((Fm - Fg - Fd) / m ) *t)^2 which is just a lot of...
  45. G

    Need help with D.E to account for air drag of my projectile

    This past weekend, for fun, I made a pneumatic air cannon, using compressed air to shoot out a small projectile at very high velocity. I'd post my video, but I have not made 15 posts on this forum. What I need to do is find as close as I can to the actual initial velocity of a projectile...
  46. R

    Energy lost due to dissipation by air drag

    Homework Statement An outfielder throws a baseball with an initial speed of 71.0 mi/h. Just before an infielder catches the ball at the same level, its speed is 85 ft/s. How much of the ball's mechanical energy is dissipated by air drag? (The weight of a baseball is 9 oz.) Answer is asked for...
  47. V

    Solving Air Drag Equation with Horizontal Velocity & Distance

    Hey guys, I am working on deriving some equations of motion for an object with air drag. I am using this site to help me: http://www.grc.nasa.gov/WWW/K-12/airplane/flteqs.html Here is my problem, at the bottom of that page they have this equation for horizontal velocity: 1. u =...
  48. B

    Calculating Air Drag for Projectiles Lab

    Homework Statement I am unable to calculate air drag for a projectiles lab I am doing. It involves shooting elastic bands and measuring the distance they travel and compare it to the theoretical distance(with and without friction). It takes 0.45 seconds for the elastic band to fall and...
  49. V

    Solving the Projectile Motion Problem With Air Drag

    Homework Statement A projectile with mass m is fired upward with an initial speed v0. If the air drag varies with the square of speed F(v)=-kmv2 show that the projectile reaches a height of h=1/2k*ln[1+(kv0^2/g)] Homework Equations F0+F(v) =...
  50. N

    Calculating air drag for a massive rocket

    Not just a little rocket that goes a 1000 feet in the air, but one that can get into space. How does one take into account that the air density grows less with altitude, etc? Anyone know of any good resources for a problem like this?
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