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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48 views

Estimation of Thickness of A Soap Bubble using the Sphere Drag Coefficient [closed]

How can wall thickness of a bubble estimated using Drag coefficient(Dc) of a sphere? It doesn't make sense to me, as we do not have ratio of inner and outer Radii neither in Dc formula nor in Reynold'...
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Reparametrize projectile motion equations with drag and lift

I know that the following equations of motion are used when describing the motion of a projectile with drag and lift: $\frac{dv_{x}}{dt} = -kv(C_dv_x+C_Lv_y)$ $\frac{dv_{y}}{dt} = kv(C_Lv_x-C_dv_y) - ...
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Dynamical system in two dimensions

I am trying to expand system into two dimensions. Dynamical system with damping proportional to squared velocity is given by Newton's eq: $$ \ddot{x}(t) + \mu \dot{x}^2(t) = 0.$$ Now, I want my system ...
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An object with mass $m$ thrown with speed $v_0$. There is gravity and air resistance. Find the speed of the object right before it falls on the ground [closed]

There is an object with mass $m$ on the ground. This object is being thrown with speed $v_0$. There is gravity and air resistance. The air resistance is given by $\vec{F}=-m\alpha\vec{v(t)}$ and $\...
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Lighter car vs heavier car, energy efficiency

I typically assumed in vehicle energy efficiency debates, the importance always in propulsion- to reduce vehicle mass. This usually implies high energy mass density fuel, like hydrogen fuel cells, ...
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Approximating drag coefficient

I've been trying to approximate the drag coefficient based on a frontal shape of an object. here's what I've come up with. We can represent the shape of an object as a function f(x) (x is length, f is ...
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What's the difference in force between lifting an object out of a viscous fluid (like honey) versus air?

Roughly, how much more force does it take to lift a stick out of a viscous fluid (like honey) than the same object the same distance in air? I'm not looking for a hard number- more like a back of the ...
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Energy lost due to air drag of a varying velocity object [closed]

How do we calculate total energy lost of an object due to air drag which is moving with varying velocity (from $v_1$ to $v_2$ m/s with an acceleration $a$ and over a displacement $s$) in air? Assume ...
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Why is the $\frac{1}{2}$ significant in $\frac{1}{2}\rho v^2 C_d A$? [duplicate]

The formula for drag force is $F_D=\frac{1}{2}\rho v^2 C_d A$. Why is the $\frac{1}{2}$ significant here? I think that the drag coefficient $C_d$ already serves the purpose. Is it for a historical ...
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Does unity drag coefficient have special meaning?

gives examples of drag coefficients of assorted shapes from 0.045 to 1.28. I understand that $C_D=\large{\frac F{\frac 12Av^2\rho}}$. Does a drag coefficient of exactly one correspond to any ...
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Equations for air drag acting on a body with both translational and rotational motion

Imagine you drop a very thick pencil. The pencil will fall with both linear velocity and angular velocity. How can we account for the drag forces acting it so as to calculate its angular velocity and ...
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What's the required area of a weightless plate in the air, to move only a set distance under given force in given time?

This discussion got started on Worldbuilding.SE; see the magical background there. At the root is a problem in pure physics, so I thought I would ask it here too. It concerns a witch who can walk on ...
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How does a ram-air parachute move forward?

I'm trying to understand the "physics" behind the flight of a ram air parachute, Do you know / how could I know, whether the main parameter that makes a ram-air parachute move forward is: ...
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Why do bullets slow down from air friction?

So intrinsically we can imagine the bullet (a cluster of particles) moving through a medium (a sea of particles), and as the cluster moves, it bumps into lots of particles within the sea and imparts ...
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Displacement time graph- aerodynamic drag

In the displacement vs time graph of an object in free fall, the parabola with aerodynamic drag is much more steeper on the way downwards of the object than the parabola in which air friction is ...
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Why is aerodynamic drag independent of mass?- intuition

What is the intuition behind the formula for aerodynamic drag and why it doesn't include the mass of the object? It seems to me that the falling object would exert a force on each particle in the air ...
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Jumping without a parachute — how much horizontal velocity can you achieve?

I am curious about the old chestnut of falling from an extreme height -- perhaps 1,000 meters or more -- and whether it is possible to convert most of the vertical velocity to horizontal, or any ...
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Is this assumption reasonable?

In physics book which I use right now proposes a simple deduction for drag equation. Almost every part of it is nice. But when deducting, it says: Whenever object hits an air molecule (which we assume ...
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Solution of the differential equation of a pendulum with a block (air resistance)

The differential equation for a pendulum with air resistance is $$ \ddot{y} + (b/m) \dot{y}^2+\frac{D}{m}y = 0 $$ What is a solution of the differential equation? I had problems to solve it.
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Projectile motion with or without air resistance

It is unclear to me if we can call a motion a projectile motion or an object a projectile if there is involved air resistance. Some sources say that a projectile is only affected by the acceleration ...
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The ball is thrown upwards. Will the work done by air resistence while going up be different from the work done when going down? [closed]

Can someone help me? Will the work done by air resistence while going up be different from the work done when going down?
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Variable Exchange $F(t) \to F(x)$? I want the value of the work done by drag [closed]

I got a nonlinear equation, which describes the magnitude of a force as a function of time, but I don't know how to calculate the work done by the force. Given: $$F(t) = kv(t)$$ with $$v(t)= \left(1-\...
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Drops are not spherical? [closed]

Surface tension tells us drops are spherical but dew drops or drops large ammount of big substance really fallapart or are not mainly a most perfect sphere. Is there hold the following and what is ...
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How to calculate coefficient of disintegration of a shot/fired Object? [closed]

I want to calculate the disintegration (losing mass) coefficient of a fired/shot snowball. To change its mass during the flight. I do not have any experience with such calculation. So I need some math ...
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Hypersonic vehicle drag from mist

Would it be possible to disintegrate a projectile using a sufficient dense gas due to drag effects. I.e. given enough drag from a gas, can projectiles be destroyed, or would it require a liquid or ...
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How does an increase in the drag force impact the drag coefficient?

After some derivation, the formula for the polynomial drag force constant equates to: $$ B = \frac{mg}{v_t^2} $$ Where B is the coefficient, m is the mass, g is gravity, and vt is terminal velocity. ...
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What is the phenomena where the drag of an object in water will reduce when reaching a certain speed?

What is the phenomena where the drag of an object in water will reduce when reaching a certain speed? Saw video a few years ago, kid school project, a high speed boat holding a wing under water, drag ...
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Confusion about whether or not force can be exerted on air

If someone is running in air, the air exerts a force on them i.e. air resistance. However, does the person exert a force on the molecules in the air during their motion. It seems very likely to me but ...
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Would dimples help a ping pong ball travel faster?

Dimples are used on golf balls to promote the formation of a turbulent boundary layer that stays with the ball longer as it travels through the air, therefore greatly decreasing the pressure drag ...
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Pressure Drag on a 2D Aerofoil even when no Separation of the Boundary Layer?

So if a 2D aerofoil is subjected to potential flow, then there isn't a boundary layer separation at any point with the surface of the object, and hence pressure remains constant at the front and back ...
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A Problem on Projectile motion

The problem statement is as follows: Two balls of masses $M$ and $2M$ are thrown horizontally with the same initial velocity $u$ from the top of a tall tower and experience a viscous drag of $-kv$ ($...
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Can the Rayleigh Drag Equation, Archimedes' Principle, and Weight be conjoined when looking at terminal velocity?

Scenario: Dropping materials of the same material into viscous liquid and changing height. Ex. stacking identical magnets. , p for density of liquid, V for volume of object Fg = mg of object In the ...
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Air resistance function when a body is thrown upwards

When a body is thrown up with velocity $v$ and there is air resistance $F=-kv$. Then while writing acceleration $a=\frac{\mathrm{d}v}{\mathrm{d}t}= -\frac{mg+kv}{m}$ , the minus sign is put due to ...
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$C_d$ is bigger at laminar or turbulent flow?

Bodies can be subjected to pressure drag or friction drag. But let's consider the overall drag coefficient $C_d$. My question is: $C_d$ is bigger at laminar or turbulent flow? This image represents ...
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How to estimate time to fall with air drag and variable density?

I would like to estimate the time that it takes for an object to fall if there is a quadratic drag force and a variable density. In a vacuum, the falling time $t_\mathrm{vacuum}$ has a simple closed-...
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How to calculate the positioning angle of a rocket for launch

I am building a model rocket. I want it to end up in a specific position. If I am taking into account the acceleration, starting position, end position, mass, and wind speed, how do I find the angle I ...
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Could one person move a floating aircraft carrier?

Could one reasonably strong person move a floating aircraft carrier? (EDIT: World's Strongest Man? [1]) Assume perfectly calm water; no ocean waves at all. Say, by pulling it with an attached rope, or ...
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Force as a function of velocity as $t$ goes to infinity, strange result

Here is the question: "A particle with mass m is given an initial velocity $v_0$ so that it moves in a straight line (you can consider it positive). It is subject only to a force that is ...
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What imparts a greater impulsive force water or land when falling from a large height

I saw a video of a situation of parachute failure , and how to increase your chance of survival. The speaker says that while heading your body tries to land on land but never on water Video link ...
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Why are drag and kinetic energy proportional to velocity squared? [duplicate]

For example, it takes a car four times the kinetic energy to travel the same distance at twice the speed, which quadruples the drag experienced by the car. This observation is described by the ...
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Are solid-state windmills feasible? [closed]

Imagine a structure exposed to wind. It is designed chemically so that a molecule striking the surface can transfer kinetic energy to electrons that are promoted to a higher energy state. These move ...
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Effects of floating oil on wind friction at sea

A delightful article in Deep Sea News illustrates the potent visual effect of "wave-stilling", as Benjamin Franklin called it. Normally, rough terrain is associated with greater wind ...
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Why does atmospheric drag speed up satellites?

I've read that old satellites slowly lose altitude when encountering the very thin atmosphere, and strangely enough they speed up. My theory is that the work done by the drag force is insignificant in ...
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Why isn't Kinetic Friction involved in uniform circular motion?

An object moving in a circular path as observed from the ground frame is moving with some constant velocity along a non-smooth surface, my question is we know that Static Friction provides for the ...
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How is suction produced?

While ago I was studying drag coefficients (or pressure coefficients, as we call them in the context of wind loads in structural engineering) and I wondered how can they be more than 1, for example a ...
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Using air resistance (drag) in Python calculation

I am simulating a free fall with a function that needs to calculate the time it takes for a particular object to reach the surface, I got this program working without accounting for air resistance.. ...
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How can I control the airflow in a car by open or closed window configuration?

What car window configuration will let air in by me and make / let it exit away from me. I have a large divider between front and back seats that covers much, but not all the plane between. People in ...
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Stokes law and speed at equilibrium

It is stated that the equation leading to Stokes law describes an equilibrium state, such as the upwards force is equal to the downward force: $$ 6\pi r\eta v = \frac43\pi r^3 (d_1 - d_2)g $$ Now $v$ ...
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Help understanding forces in non-conservative systems

This might seem like a very simple problem, but it's stumping a few of us (myself obviously included). We have been tasked with showing the mechanical energy of a particle is dissipated under the ...
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Why do two similar objects not hit the ground at different times?

The formula for air resistance is $$F_{air}=\frac{1}{2}\rho cAv^2 $$ where $\rho$ is the density of the air, $c$ is the drag coefficient, $A$ is the cross sectional area of the object and $v$ is the ...

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