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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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How does one calculate the energy used depending on the velocity and air resistance of an object

I am currently writing a paper on the Hyperloop. In the paper I want to do some theoretical calculations of how much energy is used/need to move the pods at different speeds with different drag ...
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Is there a “solid dynamics” and are there optimal shapes for it?

I am interested in designing an object that can move swiftly through a more solid medium like rock or dirt. Is there any particular kind of mechanical shape (besides a conventional drill) like a ...
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27 views

How to calculate the drag coefficient of a cyclist?

I am working on a short paper where I explore the aerodynamics of a cyclist. I want to find the drag a cyclist generates, but I do not know how to find the drag coefficient. Does someone know of a ...
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How to calculate the drag force of a cyclist and the drag coefficient?

I have a creative math assignment which my class was tasked to do. Thus I decided to create my work on physics, more specifically aerodynamics. I want to create a function which calculates Drag with ...
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60 views

Why a rope grabbed by a single end seems to follow the hand that grabs it?

Context I am thinking about the physics of the movement of a rope in the context of a person running and grabbing a rope in one hand (the other end is "free", there is nothing attached). When the ...
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Determining $v(t)$, time taken and distance covered by a plane given $a(v)$. Plus, reason why it is unreasonable.

GIVEN PROBLEM: A jet plane landing on an aircraft carrier deploys a parachute to slow itself. The acceleration achieved is $a=-0.005v^2 m/s^2$. a) If the initial speed of the plane is $60 m/s$ ...
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How to obtain the $dC_d/dC_l^2$ value from the drag polar of an airfoil?

I'm currently trying to do an initial design for a propeller. In order to do this I'm trying to use Xrotor. Xrotor allows the user to enter certain information about both the propeller geometry, ...
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36 views

Finding the drag force from the final velocity of a falling object

I know the velocities (v) of an object after it fell for respective distances (s). From that alone, is it possible to calculate the drag force at a specific moment in time? If not what else would I ...
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41 views

Where does this equation come from?

I am investigating about viscosity of fluids and I found the following equation to calculate the viscosity: $$\nu = \frac{2(\rho_s-\rho_l)\cdot g \cdot r^{2}}{9\cdot\Delta v} $$ The experiment ...
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36 views

Does mass slow down an object falling through the atmosphere? [duplicate]

If I throw two objects with the exact same shape and size, but one of them is heavier, will they arrive at the same time? We learn in basic Newtonian physics that mass doesn't influence the speed in ...
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37 views

Varying Gravity and Air Resistance in projectile motion

Salutations, I have been trying to approach a case about projectile motion considering variation of gravity acceleration and air resistance: A spherical baseball with mass "m" is hit with inclination ...
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42 views

Constant power, vehicle velocity and drag forces

I wanted to be able to understand how velocity changes while its applied a constant power. I know power can be calculated as this: $$P_t= (F_{rol} + F_{ar} + F_g)*v$$ where, $F_{rol}$ is rolling ...
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49 views

Rocket equation and drag formula

i originally posted this question over at the math section but a guy told me to switch it to here instead. i'm writing an assignment on firework rockets and their trajectory. Now of course im doing ...
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61 views

Derive formula for air resistance $F = \frac{1}{2}CAdv^2$ through dimensional analysis

I have an assignment, where I’m required to derive the formula for air resistance for a falling object. $$ F = \frac{1}{2}CAdv^2 $$ where $C$ is drag coefficient, $A$ is the cross-sectional area, $...
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Equations for an object moving linearly but with air resistance?

If F be the independent force acting on the object and D be the velocity dependent force acting in the opposite direction of F. The net force accelerating the object is; $$F − D = ma$$ where $D = \...
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41 views

Aerodynamics of cycling into a tail wind

I was looking at Steve Gribble's Cycling Calculator , and I noticed that the aero resistance was higher going 40 mph with a 20 mph tail wind than going 20 mph with no tail wind. Why is this? I always ...
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32 views

Effect of velocity upon kinetic friction

This question has been asked before... (Does the force of kinetic friction increase with the relative speed of the objects involved? If not, why not?), ...but there's a very specific part I'm ...
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65 views

Speed of a falling object

When an object is dropped, does it accelerate to terminal velocity? or is it at terminal velocity immediately?
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What forces the maximum speed of a cyclist on a steep climb?

I know that on a flat road drag is the main force, I have to provide as much force as the drag (and the friction in the drive train) produces. I can also see that the faster I ride, the harder it gets ...
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3answers
110 views

Are there any cases where Stokes law does not apply in viscous fluids?

A friend of mine and I are conducting an experiment to find the relationship between terminal velocity and radius of a sphere (i.e trying to confirm Stokes law). We are using spheres ranging from 1....
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1answer
30 views

Find the drag coefficient from a ln(acceleration) v time graph [closed]

I don't have a huge amount of information to go on, but I basically have the decay of a pendulum v time, and then taking the decay of this graph, I have a plot of ln(Theta max) v time. From this I ...
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82 views

Does free fall ever occur on the surface of Earth?

According to the definition of "Free fall", which is "Downward movement under the force of gravity only.", free fall only occurs when gravity is the only force acting on an object. But here on Earth, ...
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Rotational Motion, Kinematics, Air Resistance

When a body is thrown of height in a practical situation ( air is present ) considering air resistance is applying constant opposite force, we could calculate its speed by calculating acceleration ...
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Is there a way to calculate the time taken by a falling object to reach terminal velocity? [duplicate]

I know it is possible to calculate terminal velocity using air density, mass, and drag coefficient, but is there any way to calculate the time taken until that speed is reached (assuming air density ...
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61 views

Does the drag equation only apply to turbulent flow

I am doing an analysis of the motion of an object in air and so I'm first finding whether the flow is laminar or turbulent. From my research, I'm still a bit confused as to whether the drag equation ...
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If I push an object underwater, how long before it stops?

If I were to push an object that is completely submerged in water with a know force, how would I go about finding the distance it travels before coming to a stop given that I know the drag coefficient ...
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47 views

Is the mechanical power output of a car constant?

According to my textbook. The mechanical power output of a car is constant. My reasoning tells me otherwise though. According to a lot of pages on this forum related to the driving force of a car. ...
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72 views

I need to find the drag coefficient of a pendulum bob [closed]

Is it possible to find the drag coefficient of a pendulum bob from the damping caused on it during swinging. I will be able to measure its displacement from the point of origin and plot it against ...
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41 views

On the performance of Bolt in the 100 metre sprint - solving equation of motion [closed]

I'm looking at the following article(1) in which a mathematical model is used to describe the performance of Bolt (in general of a sprinter) in a 100 m sprint. The equation of motion is $$ m\dot u = ...
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4answers
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Why is $mg = bv$ and not $mg = -bv$?

I was given two formulas, $$F_D = -bv $$ $$F_D = -bv^2 $$ and was told that at terminal velocity, $$v = \frac{mg}{b} $$ which implies that $$mg = bv$$ $$mg + (-bv)=0$$ $$mg + F_D = 0$$ From ...
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56 views

Why wouldn't the weight of an object affect the magnitude of the drag force on that object?

I ran into trouble again with a course about drag force on skiing. This is the question, and its explanation: Which of the following factors would not affect the magnitude of the drag force on an ...
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39 views

Damped oscillations and generalized friction

I'm reading damped oscillations from the book Classical Mechanics by Landau and Lifshitz, quoting from the text - "There exists, however a class of problems where motion in medium can be ...
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Drag calculation from pressure + shear stress distribution

If I know the shape of a body, pressure and shear stress distribution over it, how can I calculate the total drag acting on it ? More exactly, can I calculate it this way: Drag = [Pressure difference ...
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4answers
77 views

Why is it much more difficult to horizontally throw a toy balloon than a football?

If you horizontally throw a sphere of radius $R$ it will feel, in this direction, a drag force due to air. Assume the drag is given by Stokes law, $F_D=6\pi\eta R v$, where $\eta$ is the air viscosity ...
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1answer
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Effect of Bodyform on Air Resistance [duplicate]

Visualize those little pictures as the front of vehicles like airplanes and trains. I wonder if I am right about my speculation below, and if so, if somebody could explain the exact reason. Sources ...
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103 views

Sign problem in projectile with drag

So recently, I've been playing around with the variables in projectile motion with drag to see how the trajectory changes. I had my ODE and solved it using separation of variables but the equation ...
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Drag force equals weight

we are doing lab in mechanics class.The task is find terminal velocity of drop of coffee filter and drag force 's constant $B$ in graphically as equation like $mg = Bv^2$ so basically drag force ...
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How could I integrate the changing location of the midpoint of a streamlined body into either the drag or reynolds number?

Because the volume and surface area is constant I am not sure how to represent the change in flow dynamics - laminar to turbulent. (sorry if this is a stupid question, I am a biologist and I can't ...
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How would I calculate the drag on a tube being pulled behind a boat? [duplicate]

lets say there's a tube being pulled behind a boat at a constant velocity (no acceleration) and I wanted to calculate the force on the rope that goes from the boat to the tube. Since there is no ...
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1answer
45 views

Why do we use $m\frac{dv}{dy} = -b(v-v_{ter})$ while determining how the terminal velocity is changing for an object falls down in linear drag force?

Why do we use $$m\frac{dv}{dy} = -b(v-v_{ter} )$$ while determining how the terminal velocity is changing for an object falls down in linear drag force . I was Jr Taylor's classical mechanics. In the ...
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29 views

Kinematics of a body in movement with air drag

Let's assume i got this body (red one) wich is moving along the x-axis. It has got two forces on it, one called $F$, which is constant, and the other called $D$ which is the drag caused by the air ...
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57 views

Why is the polar diagram of an airplane depended on weight?

Can anybody answer this question? Although aviation-related, it is in fact a fluid mechanics problem: https://aviation.stackexchange.com/questions/54192/why-is-polar-curve-of-a-glider-dependent-on-...
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25 views

What is the resistance of an object travelling through static fluid at different pressures?

I'm interested in the resistance a body feels as it travels through a static fluid in a tube (of a fixed radius), at different pressures. I would assume that as the pressure is reduced, the ...
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1answer
44 views

For a fluid travelling in a tube, if the pressure is decreased at a constant temperature, how does it affect the velocity and fluid density?

I am interested in understanding the relationship between pressure and velocity, as well as pressure and fluid density. I know that the principle of Bernoulli states that there exists a relationship ...
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2answers
130 views

Work done by air resistance

How can air resistance do work on a freely falling body on earth. then it's displacement is only due to gravity. I think Air resistance doesn't displace the body falling. So what is the meaning of ...
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Determine velocity of balloon from known Buoyancy, mass and surface [closed]

I need to know how to get velocity of weather balloon, if I know it's buoyancy force, mass and surface(diameter). I am using now $$v = 0.5t\left(\frac{F_\text{all}}{m}\right),$$ [$m$ = mass, $v$ = ...
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Questions about shapes and the reason behind the drag coefficient differences

What is the reason that a streamlined body has a drag coefficient that is lesser than the drag coefficient of a streamlined half-body, when the latter has a completely flat bottom, while the former ...
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1answer
49 views

How significant is the material in drag force calculations?

I went to Wolfram's "Drag Force Calculator" and received 4900 newtons for a cone that has a radius of 3 meters and a height of 3 meters, moving through air at a standard pressure, 15 celsius, at a ...
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1answer
33 views

Units caculation in the article don't match for reynolds numbers higher than 1

The article discusses the forces acting on a falling object in respect to the drag forces and reynolds numbers. The article suggests for varying Reynolds numbers, the force of drag equation is written ...
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32 views

Non-dimensional flux

My book states that when a flow around object is considered, Non dimensional momentum flux is defined as the drag coefficient In case of flow through tubes it states The non dimensional ...