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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Is there a difference in energy required to make 2 items with the same exact mass but different material travel the same distance whilst in free fall?

is there a difference in energy required to make 2 items with the same exact mass but different material travel the same distance whilst in free fall? Please answer for all cases of free fall: ...
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Damped harmonic motion [closed]

A metal pendulum on a 1 m string swings on Earth (g=9.81m/s^2) in an environment with negligible friction from air. The same metal ball pendulum is now placed in a container containing a mysterious ...
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Is the conclusion to this problem about terminal velocity correct?

So I've been solving problems for my upcoming classical mechanics exam. One of them had to do about terminal velocity. It presents two spheres of identical mass $m$ but where $2r_1=r_2$. Air ...
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Velocity of projectile with both quadratic and constant resistive force

Suppose we have a projectile of mass $m$ that impacts a material with velocity $v_0$. As it travels through the material it is subject to the resistive force $F = \alpha v^2 + \beta$. How can I ...
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Fall with drag - ignoring the gravitational force?

Say we have a fall while considering air resistance $$ma=mg-Bv^2.$$ It is a standard differential equation. But then I was asked what would happen, if we ignore the gravitational force $mg$. Now I am ...
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Falling Box Question

Let's say that I drop a 2D box which weighs mass m (lets say 10kg), in an infinitely large 2D space (+ time) which has gravity g (lets say 9.8), constantly pushing the box downwards, the space has ...
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Why don't bullets used in guns have sharp corner edges? [closed]

Why don't bullets used in guns have sharp corner edges? Like why are they spherical or smooth at the tip? Is it to avoid air resistance? But as my sir told that how speed we move proportional we get ...
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Which equation is more suitable when a man lifts his leg in fluid (such as snow, sand or mud), Drag equation or Stokes's law, or other equation? [closed]

When a person lifts his leg in fluid (such as snow, sand or mud), what kind of resistance/viscous force will his leg encounter in the vertical direction, which equation is more suitable? Drag equation ...
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At what speed would a wind affect a bullet? [closed]

Firing a gun loaded with the fastest bullet (.220 Swift 1,422m/s or any bullet that is super fast and excellent aero dynamics) in a close range (2cm) from the tip of an air blower. What would be the ...
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Terminal velocity of particle in medium with non-uniform velocity

assume that a particle of radius $R_p$ is moving under influence of gravity $g$ in a fluid medium of density $\rho_l$ and viscosity $\mu_l$. then the Stokes settling velocity is given as $$ \mathbf{v}...
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Airplane lift origin and cause? [duplicate]

How does an airplane get a lift? Is it due to the newton's third law or coanda effect or both? I am an amateur in this , kindly use simple terms.😅
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What would reach the ground first? [closed]

Hi I’m trying to get my head round this if a bowling ball and coin from the Empire State at exactly the same time what would hit the ground first I know that gravity = 9.81ms-2 but what else am I ...
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Why does a crumpled paper fall down faster than a flat paper? [duplicate]

It can't be because of less surface area as we know that friction is independent of the surface area
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Why d'Alembert's paradox has zero drag?

Why d'Alembert's paradox has zero drag? Even if viscosity is zero why drag is zero if there is no stagnation pressure at the back (right) side of ball? Why flow stay attached to ball surface,even ...
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Jumping out of upside down helicopter, will turbine wind cancel me out like a bloey joey?

How long would it take to cancel the speed you're going when you leap out of your helicopter, after it does do an aerial flip and is flying straight downward? I used to say, "college felt like ...
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Why do self-propelling objects decelerate when a large impulse is applied to it?

I swim frequently. Whenever I push off a wall and start kicking, I keep decelerating until a point, where my velocity stops decreasing and starts increasing again. I tried this with rockets too (in ...
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Does density affect the gravitational acceleration experienced by an object due to a larger body?

I know that under a vacuum, the mass of an object does not affect how fast it falls to zero height. I assume that is the same for density? What if there were air resistance? Sorry for the super simple ...
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What limit rocket final speed if there is no drag?

If thrust is constant and drag dont exist, speed goes to infinity or in relativistic physics to speed of light. Even in relativistic theory mass of rocket increase with speed that will just reduce ...
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Which direction will a truncated cone be pushed by airflow?

Consider the shape below, with the bottom and top faces being holes. Imagine we hold the shape in place and blow a wind into the big hole. The air will exit the small end at a higher velocity due to ...
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What is the relationship between velocity and time of an object gliding through water?

I took a video of a swimmer pushing off of the wall and gliding through the water until they come to a stop. Using some video analysis software, I was able to plot data points for their velocity over ...
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Can drag be neglected, although the object is in motion?

I was researching more about drag and why two things fall at the same time, and I came across Nasa's website (and quite a few more website) which said that, When drag is equal to weight, there is no ...
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Why is it easier to ship goods by water than by land? [closed]

It is much, much cheaper to ship goods over water than over land. (Specifically, I'm referring to the cost per unit mass of cargo per unit distance transported. I'm also assuming the large-quantity ...
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Predicting drag or drag coefficient?

Would it be possible to mathematically predict what the drag on free-falling object will be in 10 seconds (for example), if you know the current altitude, velocity and pressure? I know you can ...
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Do heavier cyclists experience relatively less wind resistance?

I am a cyclist with no physics training (beyond high school). In general, lighter cyclists with high power-to-weight ratios are the fastest, but I am wondering if there is an advantage to being ...
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Dependence of air resistance

If I drop equal volume of cotton and rock from a mountain, which one of them will have higher air resistance? I think it should be cotton, but the fact that they are both equivalent in volume confuses ...
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Stoke law determend the viscosity of liquid

In an experiment to determine the viscosity by the Stoke method. When we throw the ball into the liquid it will reach a certain mark and start recording the time. This mark what determines its ...
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Drag force proportional to square of velocity - interpretation

Consider an object with mass $m$, initial velocity $v_0$ subject to drag force of $-Kv^2$. The solution for the velocity is $$ v(t) = \frac{1}{\frac{K}{m}t+\frac{1}{v_0}} $$ and for the travelled ...
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Solving the helicopter hanging cable problem through differential analysis

The above problem is taken from the 2014 $F=ma$ contest. This question generated a great deal of controversy. At least two test takers challenged the answer, one who even tried to do the experiment. I’...
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How do you find the average velocity of a damping spring mass system?

I did some research and found out that it can be assumed that: $\mathrm{Average \ Velocity} = 0.5 \ × \ V_{max} = 0.5 × \mathrm{angular \ frequency} \times\mathrm{maximum \ displacement}$ But which ...
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Relative efficiency of airplanes and helicopters, why is this argument wrong?

I'm trying to better understand why helicopters are less fuel efficient per unit distance than airplanes. One argument I keep seeing in other questions on the topic is that helicopters actively ...
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1answer
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Predicting projectile trajectory based on only positional data

Sorry if this is a stupid question, as a CS major I'm not as well versed in physics as I would like to be. For a computer simulation, I am trying to predict a trajectory of a ballistic missile based ...
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Will fuel consumption be the same at constant speed between two engines of different power?

We have two same cars,same weights,just with two petrol engines, one has 200hp and second has 400hp.engines have same efficiency factor. In theory at same constant speed at highway of 140km/h cars ...
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Rain drop equations

Motivated by this question, I am thinking about describing a rain drop beyond the elementary physics. The principal improvement, it seems, would be accounting for the drag force dependence on the size ...
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Which object has lower drag? [duplicate]

Two same objects,only difference are parts that are paint in red,5m long,fluid air,veloctiy up to 300km/h. Which object has lower drag of these two and why(explanation)?
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Has car round back any aero advantages? [closed]

All Porsches have round back so much(top to down and also side to back) that people know to joke that car has lower drag when drive in reverse! Does so much round back has any aerodynamics advantages ...
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Why car has sharp separation edges at the back?

Most new cars that gain low drag have sharp separation edges at the back. If edges are round than wake is smaller but curvature produce low pressure, if edges are sharp wake is larger but dont have ...
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Why does something round roll down faster than something square?

Why does something round roll down faster than something square? That's a question given to me by my five year old son. So let's not get into detailed discussion about what is 'square' and what is '...
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To what extent can atoms be *specularly* reflected (in the context of high velocities in a rarified atmosphere)?

This is a follow up to earlier comments below this answer regarding orbits at low altitude. The suggestion is to try to obtain energy from the Earth's rotation to maintain an orbit with a very low ...
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How can a Kestrel hover in the wind?

Kestrels are birds of prey commonly found in Europe, Asia, Africa, and the North America. They belong to the falcon family but have a unique ability to hover in the air. You can find a whole bunch of ...
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For competitive swimmers, why does drag increase when pushing off of the wall near the surface rather than deep in the water?

I found this experiment which showed that there is the least amount of drag between 1.25 and 1.50m below the surface of the water, while there is increased drag at just 0.25m below the surface. The ...
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Why is an airfoil shaped like a teardrop?

I understand the reason airfoils are cambered on the top: to create lift. But one would assume this would result in aircraft wings having a semicircle-shaped design. Why is the cross-section of an ...
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Frictional force is proportional to the velocity

I came across the following in Goldstein Book: The frictional force is proportional to the velocity of the particle. Thus its $x$ component has the form $F_{fx}=-k_x v_x$ . Wikipedia says, ...
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Does the speed in which a gas through a medium matter?

There are two thrusters. They both expel the same volume of gas. The difference is, one has a fine stream of propellant at a higher velocity, and the other a wider stream at a lower velocity. Would ...
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Calculate velocity of a ping pong ball launcher

I'm trying to create a ping pong ball launcher based on the design of the common tennis ball launcher which consists of two rotating circular discs which rotate in opposite directions, when a ball is ...
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Solving a differential equation involving drag force and acceleration [closed]

I've undertaken a project which requires me to find a function for the horizontal velocity, in terms of time. For context, I'm studying the movement of a cannonball against air resistance and I need ...
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1answer
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Confused about what makes air follow a wing

I already asked the same question and got great answers but im also confused. One of the answers said that I can imagine that, because air over the wing has a higher pressure than the air right above ...
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Effect of side wind on the drag of a falling sphere

I just thought of a problem that seems quite fundamental but I couldn't find a clear answer or explanation. Consider a solid sphere falling in a Newtonian fluid due to gravity. It eventually reaches ...
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Propulsion power necessary to overcome drag

Say I'm riding a bicycle with a tailwind / headwind. To calculate the drag force, I'd use the relative speed of the bicycle with respect to the air. But then to calculate my power output, would it be: ...
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How fast do I need to go to run on water? [duplicate]

Well I was reading this article and I got stuck in this particular line because according to my calculations, the reaction of on my foot by the water should be $\rho A v^2 \sin^2\theta$. I am ...
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Why does Drag force equation contradicts the relationship between Reynolds number and drag coefficient?

The drag force equation is described as: $$ F_D = \frac{1}{2}\rho v^2 C_D A $$ Where the cross-sectional area of the front of the sphere is = πr^2, so we can deduce that the radius and drag ...

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