# 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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### 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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### 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 ...