What is Drag: Definition and 747 Discussions

Dragu (Hungarian: Drág) is a commune located in Sălaj County, Transylvania, Romania. It is composed of five villages: Adalin (Adalin), Dragu, Fântânele (Kabalapatak), Ugruțiu (Ugróc) and Voivodeni (Vajdaháza).

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  1. iMakeMehThings

    B Need help finding the G1, G2, etc... drag coefficient functions

    I cannot seem to find them, and I am confused as to what they are. I am trying to simulate a bullet in flight and need to calculate air resistance. I'd like to be accurate to real life and use a lookup table but I can't seem to find a graph of the drag coefficients that has an accompanying...
  2. V

    Pounds Of Explosives Necessary

    Hello! Apologies if I'm missing some information but here is my thinking so far. Had the drag force not been there, the potential energy would equal the amount of energy the explosives have to disipate to get the car to that height. However, since drag force is included it makes it more...
  3. U

    B What limits a rocket's max speed if in space drag is zero?

    What limit rocket max speed if in space drag is zero? If drag is zero and thrust is constant that mean rocket accelerate all the time?
  4. J

    I Why do bullets precess in the opposite way from gyroscope diagrams?

    1) Bullet spin causes a bullet to become a gyroscope. Specifically, bullets have their center of pressure in front of their center of mass. Therefore, when pressed, gyroscopic forces cause a bullet to spin 90 degrees instead of tumble. See this diagram: 2)The precession does not cause the...
  5. H

    B Some Questions About Drag (for ships in water and airplanes in air)

    I'm interested in the very basics of drag, both for ships in water and airplanes in air. Here's what I have so far : Flow of the medium can be laminar or turbulent. As the relative speed of the vessel increases, the more likely the flow is to be turbulent. Laminar drag increases linearly...
  6. prithika

    I Effect of vent ratio on the drag coefficient of round parachutes

    For my 12th grade school project, I'm planning to research on the effect of vent ratio on the drag coefficient of round parachutes. My idea was to make small model parachutes and drop them from a height, and derive the drag coefficient after certain assumptions. But I also thought it'd be...
  7. electrodacus

    I Equation for power required to overcome drag

    Here is the link to the equation I consider to be correct https://scienceworld.wolfram.com/physics/DragPower.html Is anyone disagreeing with that and if so can you provide a link or screenshot from a proper textbook ? The v in that equation is defined as speed of the fluid relative to the body.
  8. J

    Induced drag of ground effect-vehicle

    Model ground effect-vehicle shape like on picture fly above flat surface like floor sports hall or ice, wing end plates and trailing edge is so close to the ground(1mm) we can assume airlfow under the wing is zero and has stagnation pressure("100% ground effect"). How to calculate induced drag...
  9. J

    Does induced drag theory include the Lift = Weight condition?

    This is usual induced drag diagram. I have 2 questions: From Kutta–Joukowski theorem Fr is always perpendicular to effective airflow. 1. Does it mean for case without effective airflow(zero induced downward velocity), Fr is perpendicular to freestream airflow,so drag is zero? When effective...
  10. J

    Ideal car rear roofline angle and shape for low drag?

    What is ideal rear roofline(rear window and trunk) angle and shape(straight line, curve ..etc) for lower drag? Keep in mind if you increase angle, you reduce butt area / wake, but induce low pressure at rear window/trunk , if you decrease angle you increase butt/wake but increase pressure at...
  11. J

    I Car low average speed vs aero drag relation

    I drive car only at country roads allways at speeds 100-120km/h, no city and no idle time-heating engine etc. Why computer allways show very low average speed , 40-48km/h?I allways have feeling that this speed is too low because I allways drive way faster then this. Indeed all my friends have...
  12. J

    I Does Pulse and Glide only work with manual transmissions and a kill switch?

    When car drive uphill, gravity/weight has drag component, that is reason why you must add more throttle compare to ligther car at same constant speed uphill. So logicaly car increase fuel consumption. But if you drive downhill, gravity/weight has thrust component, so your top speed("terminal...
  13. crememars

    Wind drag problem with a ball hanging on a rope

    I drew a FBD but I feel like it's wrong because there are too many missing values. I tried this: Fy = 0 Tcosθ - Fg = 0 Tcosθ = mg T = (1.2)(9.8) / cos(25) T = 12.98 N Fx = ma Fwind - Tsinθ - Fdrag = ma Fwind - (12.98)(sin25) - Fdrag = ma I don't know how to find these missing values. I feel...
  14. J

    I Car drag coefficent vs fuel consumption link

    Car has drag coeffecient of 0.35 and drink 5L/100km, if car Cd is reduced to 0.20 and everthying else stay the same(frontal area,power,weight etc),how much will car drink? Is it possible to calcualte this or we need something more? I am interested if exist direct link/formula between Cd and...
  15. 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...
  16. E

    Potential and Kinetic energy equations including drag coefficient

    1. Golf ball initial potential energy uncertainty (110-5kg 0.01 m 0.01m/s2)= 110-9J4.31210-5=4.31210-14j 2. Golf ball initial potential energy calculation (4.4 x10-4kg 9.8 m/s2 0.609 m)= 4.31210-54.31210-14j 3.Golf ball final potential energy uncertainty ( 110-5kg 0.0 m0.01 m/s2)= 0.0 J 4...
  17. Mr Nobody

    Magnets & Eddy Current Drag help please

    Hello everyone, I'm working on a home project to create AC current, using magnets (AC Generator). I understand the principles of how to generate AC current however, I lack the complex knowledge of the physics side. I have searched and watched various Youtube videos etc, but none of them answer...
  18. aladinlamp

    I Viscous Drag of Water: Effects & Understanding

    Hi i want to understand effects of viscious drag of water in fixed cross section open channel flow. My understanding is water viscosity and channel surface create drag opposing movement of water, changing kinetic energy of water to heat. Result is warmer water and slower water flow. If the...
  19. O

    I Equipartition theorem and Drag

    If I have a many-body Hamiltonian, and I choose a coordinate x with canonical momentum p, I can say that by the generalized equipartition theorem that <p(dH/dx)> = -<p(dp/dt)> = 0 Since p and x are distinct phase space variables, and since by the Hamiltonian equations of motion the force...
  20. A

    How to Solve for Delta_h: A Math Question

    b) My question is here! 0.9v_t = v0 + a*t = a*t t = 0.9v_t/a delta_h = v0*t + 0.5*a*t^2 = 0.5*a*t^2 = 0.5*((0.9*v_t)^2)/a = where a = (-m*g + b*v)/m delta_h = (0.5*((0.9*v_t)^2)*m)/(-m*g + b*v) plugging in everything delta_h = 1.65 m which is not what the answer is. Please help
  21. A

    B Is Gravity Impacting Projectile Range Beyond Air Resistance Effects?

    Calculated maximum range of arrow at 45 degrees with initial velocity measured horizontally is of course reduced by air resistance. BUT initial velocity at 45 is reduced because propulsive force is constant and gravity reduces velocity by about 3m/sec. So not all distance loss is drag. Authors...
  22. L

    Pressure drag and the Reynolds number

    Ok, I am kind of lost in my fluid dynamics course on a specific topic. I understand the reynolds number and how it works. What i do not get:: if Re = VD/v, and if we increase V(velocity) which in turn will increase the inertial effects of the number, why is it called a pressure drag? pressure...
  23. pasta-lord

    Effect of Surface Area on the Drag Coefficient of a Parachute

    Summary:: Does the surface area of a parachute affect its drag coefficient? If so, how? I have been trying to figure out the effect of surface area on the drag coefficient of a parachute. I have designed a lab in which parachutes of different surface areas are dropped and the terminal velocity...
  24. E

    I Cosmology: Compton Drag Explained

    What is the Compton Drag in cosmology?
  25. Engineering77744

    Max L/D Ratio: Aircraft Drag Polar Explained

    Would like help as to the method rather than the answer please. Classes haven't been very clear therefore everything is self taught. Many thanks. ' The Drag polar for an aircraft is given by: CD = 0.025 + 0.08 C^2L What is the maximum Lift to Drag ratio '
  26. J

    I The CMB drag on an object moving through space

    An object moving through a fluid, such as the air, experiences a pressure drag caused by the difference in fluid pressure between the front and back surfaces of the object. Similarly, an object moving through a thermalized photon gas, such as the CMB, also experiences a drag. The cause in this...
  27. T

    The main cause behind viscous drag

    What's the main cause behind viscosity and viscous drag? Let's see it in the molecular level. Drag occurs because one molecule attracts another. And the foremost reason for which one mass can attract other is gravity. But, it's too weak in comparison to other forces in nature and at the...
  28. P

    Help with drag coefficient calculated from ballistic coefficient

    I want to make a video game about snipers and I would like it to have proper bullet physics, not something very accurate, but with "credible" bullet physics. So I need to implement a simple trajectory solver. I thought of taking into account just the gravity and turbulent air drag. The...
  29. T

    Relationship between Drag Force & Viscous Torque on USA Football

    Hello, I am a Physics undergrad degree graduate who is attempting to do a personal project involving the projectile motion of an American football in a 2D space. I want to take into account the drag force that the ball will experience and also take into account the spin of the football (in the...
  30. T

    Quadratic Drag Force: Solving Differently

    But the answers to these two questions confuses me. For the first question the answer goes like: $$m\ddot y = -mkv^2-mg$$ $$\therefore \ddot y = v\frac{dv}{dy}$$ $$\therefore v\frac{dv}{dy}= -kv^2-g$$ but for the answer to the second question we have: $$m\dot v = mg - cv^2.$$ Both questions...
  31. M

    Drag on a Supersonic Baseball (from SmarterEveryDay)

    In a recent video from SmarterEveryDay, a baseball is launched from an air cannon faster than the speed of sound. I used the video with my 2nd year HS physics class, and we put the high speed segment of the moving ball into Tracker (video analysis and modeling tool). We found that the drag...
  32. E

    Drag force on a descending sphere

    i tried a force balance around the sphere but the weight of the displaced fluid is greater than the weight of the sphere which gives a net acceleration upwards and no terminal velocity but the book says that the terminal velocity has a certain value from there the exercise is meaningless to me...
  33. BasNijhof

    Is there a way to calculate the Drag coefficient from any given object?

    Hi guys, for my final high school project I want to create a simulation in Unity (A game engine) in which you should be able to make an airplane fly with extremely accurate physics. In the regular formula for Drag is: Fd = 1/2 * ρ * v^2 * Cd * A. I can get all these things except the Drag...
  34. M

    Special Relativity Math Thing (Fresnel's Drag Coefficient)

    I am wondering if there is a typo in my textbook. Please see the attachment. The textbook says "...keeping only the lowest term in x = v/c." I am wondering if it should be "x = v/(nc)," as I circled in blue on the left side. It is a binomial expansion of the denominator. Shouldn't x be v/(nc)...
  35. T

    Lift, Drag, Magnus, Bernoulli, Tennis ball fuzz, etc.

    Hello, My background is not fluid mechanics. Yet, I am trying, very late in life (near retirement) to understand some things, now that I have time. I have always been confused about the qualitative descriptions about the role of dimples on golf balls and fuzz on tennis balls. Sometimes, the...
  36. B

    Direction of acceleration of a projectile with drag force

    First and foremost, thank you so much for your help! I'm new to Physics Forums, and this is my first post. I thought I understood the problem, but as I moved on to the subsequent parts of it became apparent that I was missing something. I set up my ##F = ma## equation as below, and solved that...
  37. Andrea Vironda

    Automotive Aerodynamic drag on a car and recovering some of that energy using a fan

    I think that driving at 130-140 km/h a car could dissipate 5-10 kW of energy only because of aerodynamic drag. Why cars don't have a fan somewhere to exploit the aerodynamic drag? For example a Pelton turbine
  38. G

    Gravity, Air Friction, Drag, 50, 60, 70, 100 miles up?

    German V2 rocket engine burn was 70 seconds. Rocket speed about 4000 ft per second. Rocket launched straight up for 3 seconds then turned to a 42 degree angle. There is a lot of counterdicting information online about how high up V2 want and how far it flew but that is not the point. Engine...
  39. A

    Power required to reach X velocity in X time with drag

    Hello, I wrote a program that adds force to a car like so: Engine Force = Power / Velocity Drag Force = -Velocity² Net Force = Engine Force - Drag Force = Power / Velocity - Velocity² I'd like to determine power based on how fast I want a car of a given mass to reach a given speed, for...
  40. cwill53

    Solving the Mechanics Puzzle of Meshcherskii: Understanding Thrust and Drag

    "Collection of Problems of Mechanics" by Meshcherskii.I see how the answer could be arrived at because each successive drag increases the number of ropes that must be used, but what I don't understand is why the thrust and drag of the tug doesn't play a role in the number of ropes required.
  41. O

    Calculating Power and Force in Cycling: Solving for Force in the Equation P=Fv

    OK, so I tried to relate the equation P=Fv to the given equation that Pave^2= 3(Pftp^2)/Nh. I put Nh in terms of distance to satisfy the requirement that the answer should be in terms of Pftp and distance by saying Nh = distance/Vave. I also substituted Pave with Fvage. (FVage)^2 =...
  42. CrosisBH

    Finding the final velocity with quadratic drag

    I chose coordinates where down is positive. So the force going up is $$F_{up} = mg - cv^2$$ $$a = g + \frac{c}{m}v^2$$ $$a = g + \frac{c}{m}v^2$$ $$a = g \left(1 + \frac{v^2}{v_t^2}\right)$$ $$a = \frac{dv}{dt} = v\frac{dv}{dy} = g \left(1 + \frac{v^2}{v_t^2}\right)$$ I used normal separation of...
  43. erlend

    Hydrodynamic drag of a rotating paddle wheel

    Hello, i have a problem that look's easy to solve but really is not. It involves a rotating paddle wheel submerged in water and i want to know the force exerted on the wheels and the torque required to rotate it. I have made a simple drawing to illustrate the problem below. I want to use the...
  44. CrosisBH

    [Computational Physics] Modeling the path of a Baseball with drag

    import matplotlib.pyplot as plt import numpy as np #constants and conditions initial_velocity = 49.1744 #m/s, book has 110mph velocity_angle = 35 * np.pi / 180 #coverted to radians because numpy only likes radians gravity = 9.8 #m/s^2 dt=0.1 windspeed = 4.4704 #m/s book has 10mph #calculating...
  45. L

    Velocity change under drag and other forces: small mass, large delta-t

    I am working on simulating the movement of small spherical objects under the influence of drag and a number of other forces that, at least for now, don't depend on the object's velocity. Normally I would sum up all these forces, including drag, to ##F_\Sigma## and update the object's speed...
  46. tanaygupta2000

    Motion involving drag force

    Since given F = -kdx/dt so I equated mx'' = -kx' which gave x(t) = A + B exp(-kt/m) hence v(t) = (-kB/m) exp(-kt/m) and using v(0) = u, v(t) = u exp(-kt/m) then I...
  47. F

    Lift and drag coefficients vs AoA graphs of a specific NACA profile

    Hello, I would like to understand know how the lift coefficient ##C_L## versus AoA curve and the drag coefficient ##C_D## versus AoA curve are determined for the various tabulated NACA profiles. Are computer simulation run for the different profiles assuming a certain Reynolds' number? Or can...
  48. 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...