# Tagged Questions

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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### How find/estimate Parasitic Area (CDA) in order to calculate V(L/D)max?

I am trying to calculate the speed which maximizes lift/drag for an aircraft. Using Carson's paper, it looks to me like the only unknown variable is "f", the parasitic area, which Carson describes as ...
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### Pressure loss in an infinite pipe

I feel lost in this problem. I know pressure loss occurs in a pipe flow due to friction. Say given a constant diameter pipe, if we keep lengthening the pipe horizontally, and static pressure will ...
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### Force dependence on velocity : Drag

I just listened to the second lecture of Leonard Susskind on classical mechanics where he discussed that force can't be proportional to velocity, since it's unable to retro-dict (predict past). He ...
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### I know that free fall in vacuum is independent of mass. But what happens in air?

Pardon me if this sound somewhat trivial to some of the highly qualified users here. So I know two objects will fall at the same rate if they are in absolute vacuum, so what I'm assuming is that the ...
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### Calculation of Drag coefficient for infinite cylinder

I would like to calculate the drag coefficient for an infinite cylinder for various Reynolds numbers. I'm using $C_D=\large{\frac F{\frac 12Av^2\rho}}$ My question is how do I calculate force ? ...
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### Magnitude of Drag force correction on a bean bag

I am currently designing a ballistic launcher for an engineering project. Our task is to propel a bean bag approximately one hundred grams in mass ten feet with the lowest standard deviation possible. ...
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### If we threw a baseball from the ISS, could we deorbit the ball?

Clearly this is a hypothetical question. Say we bring a star baseball player into NASA, prep them appropriately for a mission in space, and fly them up to the International Space Station. They go on ...
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### Can drag force and lift force be in the same direction in the following case?

In the attached picture, can I say that there is a lift force in the Y-direction, and a drag force too in the same Y-direction? $F_L$ proportional to $V_fx^2$ ? $F_D$ proportional to $V_py^2$ ? Is ...
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### Is drag force in the direction of particle motion or opposite to motion?

Suppose water is flowing in horizontal direction (positive $x$-direction) and a particle immersed in that water is also moving in the same direction. In this case, is the drag force $F_D$ in the ...
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What are the conditions at which free fall occurs? If a body is falling freely under the effect of gravity only without external resistance, the motion is called free fall. This definition gives me ...
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### 100 lbs of drag? Really? Chain running physics

Recently came across this video of an endurance technique involving the strapping of a 100lb chain to one's back and running along the grass dragging it behind. What is the true force experienced by ...
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### Do dimples reduce laminar drag across a surface?

My question is about laminar flow across a smooth surface. I have read about how the eddy currents, caused by dimples, at the surface help a blunt object travel through the air with less drag as in a ...
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### what causes airborne bodies to tilt?

Imagine a Helium-inflated oblate spheroid floating still (A). Buoyancy force cancels gravity force on Y axis. Object is tied to ground with a rope. If a wind force is applied on X axis, why does the ...
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### power of an engine with wind

I know the power of an engine to overcome air drag is $1/2 c_d ρAv^3$. If the speed of the car $25\ \mathrm{m s}^{-1}$ (relative to the ground) and it travels in opposite direction to a wind at a ...
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### Solving Projectile Motion Equation with Drag [closed]

Previously, I was helped in solving a projectile motion equation to model the velocity of the projectile with respect to distance with drag taken into account by using differential equations (which I ...
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### If there was an object such as a bucket travelling through the atmosphere very fast could the air caught in it transition to a liquid?

The question came to me after thinking of the pressure waves in front of a spacecraft during re-entry. Would the pressure caused by the air being compressed cause the air to liquefy and if so at what ...
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### Hot air balloon trajectory predictions

Hey there Physics friends! I've been struggling with what seems to be a very basic physics question. Let's say that I have wind vector for a given altitude and location, and I want to calculate the ...