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.
1,207 questions
2 votes
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How much does air in a vehicle dampen the feeling of acceleration?
You're standing on a train. The train starts suddenly, your feet are on the floor so they start moving with the train but the rest of you doesn't. You stumble back a step and catch your balance as ...
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How does static pressure increase from flow turning differ between subsonic and supersonic cases?
When subsonic flow encounters an object (e.g. a wedge airfoil), the flow gradually turns to follow the surface. Because pressure disturbances can propagate upstream, the flow adjusts smoothly, leading ...
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1 vote
1 answer
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Will the water in the garden hose move closer?
I use a garden hose to water the garden. Assuming that when I am stationary, the horizontal distance of water movement is 3 meters, but when I move horizontally at a constant speed perpendicular to ...
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1 vote
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Guns: Has anyone compiled data about the speed of bullets falling to Earth?
If there was a Gun or Shooting or Hunting SE, I would ask there. I am concerned about someone shooting a rifle, in the boondocks, expecting no risk to another person or thing. So, let's say it's a ...
1 vote
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The validity of "added mass" calculations for real fluid
When a body moves with a constant speed $U$ through a fluid, it experiences constant drag due to the fluid viscosity $\mu$, and dynamic pressure $\frac{\rho_f U^2}{2}$. The question which type of drag ...
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1 vote
1 answer
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Fluid drag and fluctuation-dissipation relation
It is known that fluid drag and Brownian motion form an example of the fluctuation-dissipation theorem (FDT). But there are different types of drags. Are all of them dissipative or not? What is the ...
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5 votes
2 answers
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Drag caused by Unruh effect
I have recently learned about the Unruh effect, and I am wondering if the virtual particles can impart momentum to “real” matter. If so, would accelerating at sufficiently high levels result in a sort ...
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1 vote
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Which Velocity to Use (Particle or Relative) in Stokes' Drag and Reynolds Number for a Particle Accelerated by a Fluid Jet?
I'm working on a problem involving a spherical particle (alumina) injected with zero initial velocity into a high-velocity argon plasma jet. The particle is accelerated by the drag force exerted by ...
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3 votes
1 answer
320 views
A brick sliding in an horizontal plane after an initial push (under Coulomb's dry friction and Stokes' drag) - part 3
A brick sliding in an horizontal plane after an initial push (under Coulomb's dry friction and Stokes' drag) - part 3 Intro This is a follow up of this question. After finding counter-intuitive the ...
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2 votes
2 answers
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Sign convention in air resistance velocity equation
If I try to solve this problem by starting with $ma = mkv - mg$ (since air resistance acts upwards and gravity acts downwards), a number of problems arise. When integrating and applying the initial ...
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1 vote
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Why is a fast moving projectile blown more by crosswind than a slow one?
I am trying to understand this surprising fact (described in Wind Doesn't Blow Bullets) that a fast moving bullet is blown by a crosswind more than if it was just dropped and allowed to fall through ...
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3 answers
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Taylor's mechanics transient term
I recently finished highschool and for fun as I wait to join in September, I've decided to tackle on some classical mechanics. In Taylor's mechanics on page 54, we first derive the position function ...
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Model of Drag on a Rotating Bar about its Edge
I saw a Stuff Made Here video on youtube where drag from rotating beam like members were slowing his motor down significantly, and I thought I would give a crack at calculating how much drag force ...
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How does drag scale with speed for a sphere?
At low speeds, drag scales as the square of the speed. This breaks down in the transonic regime, and for most vehicles drag starts increasing even more rapidly, and then actually decreases afterwards ...
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4 answers
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Why does the frontal surface matter and not just the regular surface for air drag?
Why does only the frontal surface of an object matters when calculating the air drag. The air molecules still have to flow along the complete surface right? So for example when kicking against a foot/...
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