Questions tagged [drag]

The force on a body resulting from it's motion through a fluid (gas or liquid). This force is directly opposed to the direction of travel.

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12 views

Finding acceleration from drag force/initial velocity in terms of terminal velocity

A ball is thrown horizontally with an initial velocity of half of its terminal velocity. What was its initial acceleration? I understand that being thrown at half terminal velocity means a drag ...
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34 views

When a skyscraper sways in the wind, in which direction is the motion?

Skyscrapers sway in the wind (Source here). Which direction, relative to the wind, do they sway, ignoring effects of other buildings nearby? I can imagine wind from the North blowing a skyscraper's ...
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What is the drag coefficient of a tetrahedron? [on hold]

I would like to know the drag coefficients of all of the Platonic Solids. However, I am more interested in that of the tetrahedron.
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105 views

What would happen if you drop two objects of the same shape and size but different mass in Earth's atmosphere?

The question of letting two objects fall in vacuum and the effects on gravity is discussed on this site including questions like the gravitational pull of the objects towards each other, the Earth's ...
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Physics of air flow in Kipchoge's sub-2:00 marathon

Yesterday Eliud Kipchoge became the first human to run a marathon distance in under two hours. Part of what allowed him to do it seems to have been that he had pacers running along with him to break ...
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44 views

About stoke 's formula

Why does the acceleration decrease whereas velocity increase for a freely falling spherical body inside a viscous liquid
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53 views

Why is the body of the rocket so long and does it effect the flight?

so my qustion is that why are rockets body so fricken long it is crazy all the rockets body are so very long and I need an answer to the question please tell me it is for science and i really need ...
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139 views

Numerical method for first-order non-linear differential equation

So I'm modeling a cycler on a 1000 m race track using the equation $$\frac{dv}{dt}=\frac{P}{m}\left(\frac{1}{v}\right)-\frac{k}{m}\left(v^2\right)-ug$$ where $P$ = power, $m$ = mass, $v$ = velocity of ...
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How does this toilet lid work?

After further reflection after closing the lid on my toilet, I noticed it exhibited a behaviour that I can't explain. When you let the lid fall, it falls at a constant speed regardless of its angle. ...
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Drag coefficient for the fin of a model rocket

I am working on a 1D model rocketry simulator that accounts for drag. I have been looking online, but unable to find the typical drag coefficient for a fin. Would anybody happen to know what it is?
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How would one represent/model the effect of air resistance on horizontal motion? [duplicate]

Evidently, there are formulas that allow us to represent the effect of air resistance on the velocity of an object in free fall but how would one calculate the effect of air resistance on horizontal ...
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34 views

Damped Oscillation and Period

In my school experiment, I wanted to measure the gravitational constant ($9.81 \ m/s^2$) by using a pendulum. If we take into account the damped oscillation (i.e. friction forces), does that affect ...
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If an object falling at terminal velocity is pushed sideways, does it slow down vertically?

For reference, I'm using this equation for drag $$d = c \times {\rho \times v^2 \over 2} \times a$$ And this one for finding terminal velocity $$v = \sqrt{2 \times m \times g \over \rho \times a \...
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Dominant component of drag in a streamlined body (sounding rocket) at 0.8 Mach

We are currently working on CFD solutions on ANSYS Fluent for the drag on our sounding rocket. We are modeling its drag profile through out its velocity range. We currently hit a top speed of approx ...
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How to calculate speed from time with changing exponential forces? [closed]

I'm making a physics-based game and I'm having trouble understanding how to implement exponential drag equations into an acceleration model so I can have a variable timestep between physics frames and ...
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28 views

On the microscopic description of a steady electric current

In Purcell's Electricity and magnetism, page 137, the author derived a formula describing the average velocity $\overline{\textbf{u}} $ of positive ions inside a conductor, a gas made of neutral ...
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33 views

Heuristic derivation of air resistance - why should the velocity of the air be equal to the velocity of the car?

David MacKay gives a heuristic derivation of air resistance of a driving car in his book Sustainable energy without the hot air. He starts with a tube of air with the cross sectional area of the car $...
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Air penetration of filter in pipe with fan

Air is forced down a pipe by a powerful fan. A filter with considerable wind resistance can be alternately mounted inside the pipe at either end. Will the same amount of air throughput occur with the ...
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How can I find the initial velocity of a projectile from its range, when accounting for air resistance?

I'm trying to find the initial velocity of a projectile based on it's range. I know how to use kinematic equations to do this when air resistance is ignored, but I'm not sure how to take into account ...
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Why doesn't my flight aerodynamics maths work? [closed]

Context: For some context, I'm a game developer and I'm building a flight sim game. My goal is to have realistic flight physics -- not arcade physics. I'm having issues with the maths -- it is not ...
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53 views

Motion of a body falling in resistive medium [closed]

Obtain the equation of motion for a particle falling freely under the action of gravity under a resistance which is directly proportional to the square root of velocity. Describe the motion and find ...
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60 views

Projectile with linear drag [closed]

A particle with mass $m$ travels with speed $v_0$ and angle $\theta$ compared to the horizontal ground. Air resistance given as $F_R = -m \alpha v$, where $v$ is the particle's speed, is working ...
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Drag force on the thin string loop rotating in air

I'm trying to figure out what is the drag force per unit of length on the circular string loop rotating in air around its symmetry axis. In particular I'm interested how this force depends on the ...
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79 views

Free fall movement with air resistance [closed]

For small free-falling particles in the atmosphere, the air resistance is proportional to the velocity (orienting the y axis vertically downwards, is of the form $-\rho y'(t)$, with $\rho > 0$. ...
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Do flat plates result in less drag than concave surfaces? [duplicate]

Do flat plates (A) result in less drag than concave surfaces (B)? Intuitively, i think flat plates produces less drag than concave surface because the concave surface makes the fluid move backwards, ...
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Why do we consider the viscous force to be tangential?

Is it that since it is a friction force, it needs to be tangential as other friction forces like kinetic friction and static friction forces are?
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74 views

Will arrow from traditional longbow will be dangerous if it is falling from above?

Let's imagine commonly seen in movies and video games "rain of arrows". Archers shoot up to hit enemies behind the obstacles, for example. As Brittanica states: “The best longbows were made of ...
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Why can't $U=b\mathbf{v} \cdot \mathbf{r}$ be considered a potential for the drag force ${\bf F}=-b {\bf v}$?

Consider the function $U(\mathbf{r},\dot{\mathbf{r}})=b\mathbf{r} \cdot \mathbf{v}=bx\dot{x}+by\dot{y}+bz\dot{z}$, where $b$ is the drag coefficient. Why can't this be considered as a potential energy ...
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Resolve Drag into Vector Components

Assume you have a sphere travelling at a velocity of $30$m/s, at angle $30^\circ$ relative to the local horizontal plane. For the purposes of the below equations please ignore more complicated ...
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44 views

Finding displacement by integrating forces that vary with velocity

I have a body that is being affected by forces, some of which are invariant ($F_i$) and some of which vary with velocity ($F_v(v)$). Given that $F=ma$ (where $F=F_i+F_v(v)$), how do I integrate this ...
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Drag force as a function of shear & normal stresses

I would like to understand the relationship between the drag force of an object in a fluid and the microscopic interactions between the object and the fluid particles. Specifically, I would like to ...
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29 views

What's the “cause” of damping coeff. in springs?

What's the "cause" of damping coeff. in springs? Air resistance, friction?
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36 views

Deriving terminal velocity

In my book (Young and Freedman's University Physics) they derive terminal velocity where and use these steps: ...we must find the relationship between velocity and time during the interval before ...
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104 views

Is the physics behind planetary travel simpler than atmospheric travel?

I've been watching a bunch of documentaries lately and had a question that I couldn't really figure out the answer to online. When spacecraft travel through space, are the equations and physics used ...
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219 views

Generating lift by Naruto running

"Naruto running" is running with your arms behind you (pictured above). Many characters in the Naruto series are superhuman and can run way faster than a normal human. I thought that they run like ...
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Why can't we use air pressure to recharge an electric cars battery

If we use energy to accelerate a vehicle, a lot of that energy is lost to drag and friction, especially in an electric vehicle. Why can't we harvest some of that energy using an alternator and some ...
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63 views

Flight time of spherical bullet fired horizontally versus dropped vertically / effect of crosswind on spherical car

Would a spherical bullet fired horizontally from a musket stay aloft longer than a spherical bullet dropped from the same height? I know two similar questions have been asked (Will a bullet dropped ...
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Friction at high speeds

I am reading a book which mentions that frictional force is not exactly proportional to the normal force at high speeds. Quoting: Once the bodies slip on each other frictional force is, $kN$. This ...
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57 views

Is it possible to find $\mathbf{v}$ explicitly when $\mathbf{F}$ varies with $\mathbf{v}$?

I have the following problem (NO, this is not to ask for a solution to this problem). A block is placed on a plane inclined at an angle $\theta$. The coefficient of friction between the block and ...
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37 views

Why is the velocity in the horizontal direction constant for 2D projectile motion?

For 2D projectile motion, why is the velocity in the horizontal direction constant? I learned that we neglect air resistance, but why? And isn't there horizontal acceleration at the beginning when ...
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33 views

Damped harmonic oscillator's maximum displacement [closed]

I want to know the maximum displacement $x_0$ of a mass $m$ on a spring with spring constant $k$, in the case that the system is damped with damping constant $c$, and where the initial velocity $v_0$ (...
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193 views

Why is the drag force proportional to $v^2$ and defined with a factor of $1/2$?

$$Drag = \frac{1}{2}C_d \rho Av^2$$ I understand that the strength of the drag depends on the density of the fluid the body passes through, the reference area of the body, the drag coefficient, and ...
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55 views

Effect of air resistance of the period of a pendulum [duplicate]

Does air resistance increase or decrease the period of a simple pendulum?
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34 views

Calculate the kinetic friction velocity vector from the kinetic friction force in a simulation

I am doing (programming) a simple kinematic 2D simulation on blocks. The idea is that the block will have a force applied. 1) From the force and mass I calculate the the acceleration vector (will ...
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42 views

Why is it easier to catch mosquitoes with your hand when your hand is wet?

Recently I've noticed that it's significantly easier for me to catch a mosquito with my hand if my hand is very wet (e.g. from having washed my hands and not yet dried them, or from being in the ...
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High velocity mushrooms?

So y’all know meteoroites burn up in our atmosphere I’m looking for an equation or something that will allow me to calculate how fast a substance can move before it starts to burn up. Specifically I’m ...
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Does air resistance have a greater affect on longer pendulums than shorter ones due to the greater exposure it has to air?

I'm thinking, because longer pendulums travel for a greater time period through the medium of air, air resistance will have a greater affect on the pendulum bob (and string) and so the angle the ...
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91 views

Is Verlet method suitable for to solve projectile motion with quadratic drag?

Consider the following non-dimensional equations of projectile motion in presence of air resistance, I understand it can be numerically solved using the mid-point method, but can I also use Verlet ...
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84 views

Projectile with air resistance from a given hight

Objects take same time to fall a given height independent of their horizontal speed when air resistance is ignored, is this also true when air resistance is not ignored? In presence of air resistance, ...
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Davis formula application

So I stumbled upon the Davis formula for trains while doing some researches about my project but I don't know how to apply it (programmatically) : Let's say for example this variant : $$R'=1.3+\frac{...