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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The question is about the forced damped oscillation?

A spring-mass system with m = 4kg and k = 35 N⁄m is forced to oscillate by an external harmonic force represented by (3.78N)$\sin\omega t$. Plot (schematically) the amplitude u0 versus ω ωn. Indicate ...
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What is the relation between hydrodynamic drag and buoancy force?

Is hydrodynamic drag just the overarching study of liquids in fluid whilst buoyancy force is the upwards force acting on the object? I really do not know much about this topic.
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Could Candide Thovex have avoided a crash by maximizing vertical air resistance?

NOTE: This is a very "practical" question and involves quite a lot of estimation. I'm sorry if this is the wrong place to post this question. If it is, please comment where I could post it ...
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Ball thrown faster than terminal velocity

I recently read about the property of terminal velocity for objects and I got a doubt when doing so. If from a very tall building I throw a ball faster than terminal velocity downwards will the ball ...
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Why does a spear or a javelin turn in the air?

In videos of the javelin throw, the throwers consistently seem to grip the spear at the center of mass and launch it by imparting it an initial velocity. What causes the javelin to turn around an axis ...
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Intuition on Different SI Units and Squaring Decimals (Beginner Question)

So this is a very basic question. I am certainly not in grasp of some key aspect of physics equations here. I hope someone will be able to help me out. Here is the equation for drag force: $$F_{D}=\...
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Hamiltonian for multidimensional dissipative system

I am trying to find hamiltonian for system described by EOM $$ \ddot{x}(t) + \beta \dot{x}^2(t)\sqrt{\dot{x}^2(t)+\dot{y}^2(t)} = 0, \\ \ddot{y}(t) + \beta \dot{y}^2(t)\sqrt{\dot{x}^2(t)+\dot{y}^2(t)} ...
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Has it been researched whether there exists a shape that can undergo zero resistance in a fluid of zero viscosity and has no sharp edges or corners? [closed]

I know almost nothing about fluid dynamics. After having read this answer, I'm guessing that tear drop shape has those properties. It has zero resistance only because the tip at the back end is ...
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Falling body with drag [closed]

I was doing a question and I couldn't figure out the answer, when I checked the worked solutions it did a thing and I'm not entirely sure what I am missing. The general gist of the question is as ...
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Drag coefficient for tilted plane

I'm trying to calculate the drag force for a thin rectangular plate with dimensions $L$ x $d$, like shown in the image below, with air flow (approximately) perpendicular to the plane defined by the ...
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I calculated the drag coefficient of this object to be 0.57. Shouldn't it be higher since this object has a lot of aerodynamic drag?

This is a cupcake liner with a mass of 0.23g I researched those drag coefficients for non-streamlined objects can be 1 or more, hence I am a bit surprised about the result I got. The angled sides on ...
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Is the cross-sectional area of this object just the area of the 'top circle'? or do the angled sides and height matter?

The diameter of the top circle is $0.08m$, diameter of base is $0.06m$, and height is $0.018m$. I'm trying to calculate the drag coefficient of this object and hence need the frontal projected area, ...
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Is there a way to solve the following differential equation for a sphere rising in a fluid?

Given the boundary conditions, how do I find the analytical solution (for the velocity) of the following expression: $$ \left(\frac{2}{3} \pi \rho_f a^3 + \frac{4}{3} \pi \rho_s a^3\right) \frac{d ^2 ...
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Maximum height for Terminal Velocity to be reached for a certain mass?

I know the terminal velocity equation as: V^2=(2mg)/((CdAp) I also know that v^2 = u^2 + 2as. Assuming the object's terminal velocity is also its final velocity, and knowing every other variable in ...
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How did the derivative shift? (Turbojet Thrust Equation)

While deriving the Turbojet Thrust Equation this is what the author does $$F=m\cdot a$$ $$F=m\frac{\mathrm{d}v}{\mathrm{d}t}$$ $$F=\frac{\mathrm{d}m}{\mathrm{d}t}v$$ $$F= m^*\cdot v$$ (where $m^*$ is ...
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Why do fans spin backwards slightly after they (should) stop?

Today, I've decided to observe my PC fan as I shut the computer down. The fan slowly lost angular momentum over time. What I've found really interesting is the fact that the momentum vector change did ...
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3DOF Rocket Dynamics for an LQR controller

I'm trying to define a simplified model of a rocket to implement an LQ regulator. What I need is the translational dynamics on the earth's inertial frame and the rotational dynamics in the body frame. ...
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Calculating Speed of bicycle down a hill or coasting to a stop

I'm working on trying to employ physics into a bicycle training app and I'm using the equations from http://gribble.org/cycling/power_v_speed.html to convert power (from the indoor trainer or power ...
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Is there a relationship between the initial length of a pendulum that is released in air, and the amplitudes half-life (defined in post)?

If I were to release an underdamped pendulum right now in earth's regular atmosphere, factoring in air resistance, is there a way to plot the motion of the pendulum using a regular function? Also, ...
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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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