# What is Air resistance: Definition and 415 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. ### How does a difference in air pressure induce a force?

Another likely very basic question from me Suppose I pinch a piece of A4 paper and pull it up, at a velocity of let’s say 1 or 2m/s (i.e. order of magnitude 10^0). The paper, of course, encounters air resistance / drag as it moves through the air, but there’s also a (larger) force that is...

I'm building a model as shown below (side, front, back). In order to measure its air resistance I will be mounting it on temporary ice blades (Green) and driving it down a long skating rink. The model has a pressure sensor incorporated into the motor / propeller assembly and a GPS unit to...
3. ### I Gyroscopic precession of a spin-stabilized bullet

Hi! I am trying to understand the physics behind the gyroscopic phenomenon called spin drift. Spin drift occurs to bullets that are spin-stabilized over the course of their flight. Spin drift starts with an induced rotation in a spin stabilized bullet. As a bullet flies through the air...
4. ### Vertical projectile motion with quadratic drag (sign convention)

I am attempting problem number 2.38 from John R. Taylor's Classical Mechanics and I am not getting the correct answer. My procedure is as follows: Equation of motion (taking up as the positive direction): $$m\dot{v}=-mg-cv^2$$ Now to find ##v_\mathrm{ter}##, the terminal velocity, we consider...
5. ### How to calculate the wind force acting on a water drop?

TL;DR Summary: I have a water drop falling with a constant velocity ##v##, since ##mg=\frac 12 C \rho S v^2##. Wind is blowing with a velocity ##u## only in a horizontal direction. What will be its force acting on the drop? I would use this equation ##F= \frac 12 C\rho S u^2##. When I want to...
6. ### Need Help to Understand an Equation for Air Resistance

I don't understand what the gamma letter in the equation is supposed to represent.
7. ### Air Resistance Question -- Dropping a tennis ball and a feather....

I thought the one with more mass would fall faster
8. ### 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...
9. ### Resistive force exerted on a sphere (air resistance)

i don´t understand the question
10. ### Launching a Projectile with Air Resistance

Mentor note: Moved from a technical forum section, so Homework Template is not present. Hello Physics Forums members, I am a student in AP Physics C and I was just working out the range of a projectile when air resistance is non-negligible. As of right now I'm going to use the linear model of...
11. ### B Does air resistance have a max value?

I know that friction on a surface has a maximum value. When an object is pushed with a force greater than the maximum friction value, the object will move. But when a free-falling object falls from a height, does air resistance have a maximum value as well?
12. ### Air Resistance Problem: Dropping two balls with different masses

I am not sure how to even start this problem.

14. ### Tension in rope for non-uniform circular motion with air resistance

I'm trying to solve this problem using an rtz coordinate system, and Newtons second law. I know that mar = (m(v)2)/r. I'm failing to understand how mg and the drag force affects the solution and how I would set it up. I know if it was at the bottom of the circle that mg would be added to the...
15. ### Vertical flight with air resistance

I suppose the trick in this question is to realize that the drag acts in opposite directions when the ball ascends and descends and that the ball actually takes less time to rise and more time to fall than normally. I make a small sketch of the problem alongside. Attempt : The total time of...
16. ### Calculating air resistance for a cart rolling down a ramp

I am doing a physics lab where we are supposed to calculate air resistance and find the impacts of velocity and cross sectional area on air resistance. For the experiment, we rolled a cart down a ramp and measured data using Pasco Capstone software. When rolling the cart down the ramp, we...
17. ### Is Air Resistance Negligible in Projectile Motion Experiments?

Total acceleration equaled = -9.81
18. ### Quadratic air resistance clarification

Hi all, I've been trying to follow a question I came across on a website. And I'm able to understand everything up until the separation of variables for solving the differential equation and coming to a solution with arctan. But there are a few things that aren't explained that I was hoping...
19. ### Solve this integral involving a quadratic and linear air resistance equation

Hi, I'm trying to solve this integral and then isolate V, but I can't get the right answer. I don't know where is my errors. I probably muffed the integral. ##-bv -cv² = m\frac {dv}{dt}## ## \int_0^t dt = - m \int_{Vo}^v \frac {dv}{bv+cv^2} ## I get this after the integration ##t =...
20. ### Parent needing help with a velocity question including air resistance

I'm a parent and have no idea, just looking for help please
21. ### B Testing the effect of Gravity at home....

Hi ... air resistance is the reason that objects of different mass fall to Earth at different speeds. In a vacuum all objects fall to Earth at the same rate regardless of mass. OK - I get it but all the experiments that illustrate this tend to rely on tall buildings or massive vacuum chambers...
22. ### Net forces on a boat (propulsion, water and air resistance)

2500 N [south] + 3200 N [south] = 5700 N [south] 5700 N [south] - 6000 N [north] = 300[north]
23. ### Help with adding air resistance into my projectile trajectory function

Hey, I am working on a video game in which there will be archers who have the ability to shoot at enemies. My game is two dimensional and I am trying to calculate the angle at which the archer, given an initial velocity, has to shoot in order to hit the target perfectly. I came up with the...
24. ### Regarding the work done against air resistance

Here is the question: I have correctly calculated the power produced by the thrust force (P = Force x Velocity = 9.0 × 104W) , the work done by the thrust force over 3 minutes (W = Power x Time = 9.0 × 104 × 3.0 × 60 = 1.6 × 107 J) , and the gain in potential energy over this period (mgh =...
25. ### Deciphering this problem statement: Air resistance on projectiles

I am struggling with our equation and where to plug in my velocities and forces? After looking at my book I don't understand why p(t) would be where I plug in force, and why variable "t" is where we plug our velocity in? When the problem says "what happens if you try to use a polynomial of...
26. ### Modeling a ball thrown vertically including drag from air resistance

So I'm trying to figure out how to model a ball getting thrown vertically with the starting velocity v_0. So I've come up with a differential equation which I'm pretty sure is correct: Where D is a constant. So far so good. My problem is solving this. This is my attempt: And when i do this...
27. ### Find the time when the projectile runs into the hill (with air resistance)

vy=vter + (vy0 -vter) e-th/τ where tau=m/b EQ 1 Okay, for part a, I used Eq 1 I let vy=vy(th)=0 --->The reasoning is that the projectile would stop moving for a short time when it hits the incline, but I have a feeling that reasoning is faulty I let vy0=v0sinθ Then the equation became...
28. ### Zero Friction on the Moon: Driving at Constant Velocity Without Air Resistance

Suppose we are driving on moon (I mean there is not air resistance) at a constant velocity. Suddenly the car goes on an icy land (the friction is zero). What happens? In other words, if we drive at constant velocity and there isn't air resistance, Is there any friction force between tires and...
29. ### Why is my simulation of projectile trajectory with air resistance wrong?

Hey! This started very harmless... A friend and I were throwing stones in a lake. Mine didn't get very far, he was teasing me "What was the ideal angle again?". Of course, I know it should be 45°. I replied in jest: "That's because I'm considering air resistance!" Then we had a discussion what...
30. ### Angle required to hit coordinates including air resistance

Hi, I know I've asked this before but I didn't manage to solve the problem before. To give context I'm trying to find the angle to hit a target with given coordinates from my current location in a particular game. (I'm modding the game) I can do it with zero problems when not including air...
31. ### Calculating a velocity formula using air resistance

Yeah, not sure what to do
32. ### Why air resistance has less force than gravitation force in free fall?

Why air resistance has less force than gravitation force in free fall? If Egg is fall from a nest of tree, while falling, it has less magnitude of air resistance than gravitation force. Where net force is not equal to zero.
33. ### [Air resistance of vehicle] Can anyone me?

I checked the answer, and it is not correct. Is it something wrong?
34. ### Impact of several variables on resulting projectile motion trajectory

I was told to generate these variables (m, C, alpha, wind velocity) normally distributed and compare the random data with the result and then tell, which of the variables has the most impact. Here I am stuck, tried to compare variances, kurtosis and skewness of the data (the original variables...
35. ### Show that the terminal speed of a falling spherical object ....

To write ##v## as a function of time, I wrote the equation ##m\frac{dv}{dt} = c_{2}v^2 + c_{1}v - mg \implies \frac{mdv}{c_{2}v^2 + c_{1}v - mg} = dt## To solve this, I thought about partial fractions, but several factors of ##-c_{1} \pm \sqrt {c_{1}^2 +4c_{2}*mg}## would appear and they don't...
36. ### Rolling Marble + Air resistance = Displacement?

A marble rolls down an inclined plane with an angle of elevation of 5 degrees, roughly 4.9sin(5)m/s/s, and at normal pressure temperature NPT what would I need to add to S=1/2 at^2 to include the air resistance considering the marble is a sphere with a radius of 0.85cm and mass of 20g. The whole...
37. ### Drag Force Acting on an Object with Respect to Velocity

Homework Statement The final velocity of an object falling through air from various heights is given. From this, can you derive an equation for the drag force acting on the object with respect to velocity? Homework Equations Maybe relevant? Wno drag$$=mgh,$$ Wreal$$=\frac{1}{2}mv^2,$$...
38. ### Varying Gravity and Air Resistance in projectile motion

Salutations, I have been trying to approach a case about projectile motion considering variation of gravity acceleration and air resistance: A spherical baseball with mass "m" is hit with inclination angle $\theta$ and launching velocity $v_0$, then, the wind has a drag force equals to ##F=kv##...
39. ### The dropping of two identical balls without air resistance

I was thinking about this and couldn't really figure it out. You are standing on a cliff and you have two identical balls. In this case, air resistance is to be ignored. The only thing different is that you throw the ball horizontally at different speeds. Let's say you threw ball one at a speed...
40. ### Free falling ball with and without air resistance

Homework Statement A 2 kg ball (k factor of 0.02 m-1) is in free fall. The initial downward velocity of the ball is 12 m/s. Find the difference in displacement after 1s both with and without air resistance. Homework Equations vf = vi + at y = yi + 1/2(vi+vf)t y - yi = vit + (1/2)At2 - (1/3)Bt3...
41. ### Bungee jumping dynamics assignment

Homework Statement A formula has been determined: d=l+h+ (l(SRT(m(m+150))+m)/75), where d is the depth jumped to, l is the length of the rope, h is the height of the jumper and m is the mass of the person. The question is: At present, the model does not include air resistance. Show and discuss...
42. ### Air resistance in projectile motion

In lower-division physics classes, air resistance is usually ignored to make the mathematics of projectile motion easier to understand. When air resistance is included, it's often stated that at lower velocities, air resistance is proportional to the velocity of the object, Fair ∝ kv At...
43. ### Air resistance - freefall and horizontal projectile motion

We have two identical balls sitting at the same height. One of them is released without applying any force (it falls freely) and the other one is given a non-zero horizontal velocity. Which of them will hit the ground first? The force of air resistance is proportional to the square of the...
44. ### Air resistance differential equation

Hello all, I want to say thank you in advance for any and all advice on my question. My classical mechanics textbook (Marion Thornton) has been taking me through motion for a particle with retarding forces. The example it keeps giving is: m dv/dt = -kmv which can be solved for: v = v0e-kt...
45. ### I Integration - Projectile Motion w/ Air Resistance

I"ve seen several texts that say something like this: Our equation of motion along x is dvx/dt = -g(vx/vt) Integrating this, we obtain equation 178 at this link (pretty near the top; sorry, but I can't figure out how to put the equation here). It's from FitzPatrick's online notes for...
46. ### Air resistance: cylindrical rotor in stator with air gap

Hello, I am currently doing research on the aerodynamic properties of a rotating cylinder in a cylindrical housing. The cylinder represents a rotor in a electric motor. The air gap between rotor and stator is about 0.5mm. I'm looking for a theoretical analysis and calculation on the...
47. ### Velocity of a football with and without drag

Homework Statement A professional thrower projects a football straight up in the air. 1. Assuming there is no air drag on the football, find the speed of the football as a function of height as the ball goes up. 2. Assuming the air drag on the football varies linearly with speed, find the speed...
48. ### Speed, energy, power and air resistance

What is wrong here. If I double speed drag will be 4 times higher. The engine needs to put out approximately 4 times more power. Energy consumption will be 4 time higher for a specific time period. However if it is a fixed distance I will arrive in half the time an the energy consumption will...
49. ### Need help understanding air resistance lab (coffee filters)

Homework Statement Homework Equations Equations posted in pictures attached The Attempt at a Solution I haven't attempted it yet because I am confused about something. If the-cv^2 case is for objects that hit terminal velocity at the fastest rate, why are my graphs showing that I should use...
50. ### Is jumping up in a falling elevator possible?

Imagine that you are using an elevator and - due to some cause - all of the cables supporting it cracked and the brakes were not engaged - the elevator is in a free fall. Now, would it be technically possible to jump in that elevator? Jumping requires the force of reaction of the ground, this...