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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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105 views

### Train Physics Simulation

It's my first time asking here so bear with me. I'm a computer scientist, and I'm working on a train simulator project. I'm having quite a difficult time understanding all the physics and formulas ...
36 views

### Fuel efficiency of supersonic planes

I stumbled upon an interesting plot; in particular, the dependence of wave drag on the Mach number: It is curious to see that the drag coefficient drops so abruptly in the supersonic regime, but I am ...
22 views

### Individual air molecule momentum exchange

Background: Looking at this illustration about solar radiation pressure on a perfect reflective surface, incident photon exchanges its momentum to the slanted surface which provides a reaction force ...
84 views

### How do you find the minimum height to open a parachute for a safe landing?

What concepts/formulas can be used to find the optimum/minimum release height of a parachute?
5k views

### What happens when the drag force exceeds the weight of an object falling into earth?

Let's say a meteor is coming towards earth. It's not accelerating, but it does have an initial velocity. This meteor is shaped so it has an insane amount of drag, enough to even exceed its weight (not ...
74 views

### Why the book falls faster than a feather, dropped from the same height? [duplicate]

If I dropped book and feather from same height. Why book falls first, however book has more windage(air resistance), more area(square) than feather?
120 views

### Why can I throw a larger stone farther than a smaller stone?

Recently I was throwing stones(don't ask me why) when I noticed that there seems to be an optimum weight of stone so that it travels the farthest. If I generate the same amount of force each time(and ...
12 views

### Can't find coefficient for my IVP

In my problem I have to set up an IVP and model freefall with air resistance before the bungee starts being pulled on. Beta being my airresistance coefficient. I have: $$mx'' + \beta x' = f(t) = 0$$ ...
62 views

### Why is the rudder of a ship shaped like a wing?

I don't understand why lift gives an advantage, it could be working the same even if it was just flat.
38 views

### Drag Coefficient of a rounded nose cylinders

According to this page The drag coefficient of a rounded cylindrical bodies is given by this graph Then the drag coefficient of a cone for a half vertex angle ε is given by this graph. How can ...
22 views

### Viscosity from terminal settling velocity of a sphere

I don't have an attempted answer to this question because I don't really know where to start. The Tip says to start from a force balance for the sphere, but I'm not sure on how to do that. I know ...
139 views

### How to find drag of a cylinder?

How can I find a drag on the cylinder placed in uniform water flow, if I know a velocity field around it?
45 views

### Coefficient of drag past a cylinder

I have a lab assignment to determine a drag coefficient of a cylinder perpendicularly submerged in water. I have a measured velocity field and cylinder diameter. How can I find Cd? (I heard of a ...
68 views

### At what speed in air would a solid object turn to plasma?

Just curious, friction can heat up what ever is moving. The faster something moves the quicker it heats up. Is it possible in the perfect scenario to turn a speeding solid object to plasma through ...
49 views

### Which ball touches the ground first? Different explanations

Two balls with the same shape and volume but very different masses are dropped from the same height WITH air. The heavier ball should land first, but is it because of terminal velocity (see this ...
66 views

### Does cross-sectional area affect the air time of a vertically thrown object?

Factoring in air resistance, I have two objects A and B of identical mass, however have different cross-sectional areas. A has a larger cross-sectional area than B. If I throw both objects directly ...
92 views

### Derivation of the wind load formula

I am trying to derive the wind load formula: $F_d = \frac{1}{2} \rho v^2 A C_d$ in which I assume the drag coefficient to be equal to 1. My starting point is that the momentum of a rectangular wall ...
54 views

### Where exactly does the drag force come from when using eddy currents?

I read the Wikipedia page on eddy currents and the explanation for braking confused me At the leading edge of the magnet (left side) by the right hand rule the counterclockwise current creates a ...
58 views

### Does damping force depend on frame of reference?

I learn that damping force with regard to forced damped oscillations is given by F = -bv where is the velocity of the object measured from ground frame. Suppose we are in a frame which is moving with ...
26 views

### Force applied by horizontal wind on object

Hello, I have a question for a project I'm currently doing: In a tunnel with no gravity, there is a constant wind blowing through. A sphere in the middle of the tunnel is completely motionless to ...
92 views

### Calculating magnetic strength required to hold an objects weight + wind speed?

Note: I'm a bit new to this subject, so I'm looking for some general answers, ballparks, and direction to continue my research. Scenario: I have three electromagnets capable of X amount of holding ...
42 views

### The force of wind on baseball

Does anyone know of an equation that I would be able to use for the force of wind acting upon a baseball? I am working on the projectile motion of a baseball with air and wind resistance. I have the ...
39 views

### Wind Force of a projectile

I am currently working on a program that models the projectile motion of a baseball with air resistance and wind acting upon it. However, I cannot find the equation to calculate the force of the wind, ...
64 views

### Drag of flat plate at any orientation in 3D

I am trying to calculate the force vector on a flat plate caused by wind, when that plate is not perpendicular to the wind. Imagine a sailboat, and assume that its sail is a rectangular flat plate. ...
72 views

### Parabolic motion of a projectile

During a conference I have listened that an employee of an armed force, he has said that when a projectile fired from a gun upwards, it is very dangerous because when the projectile descends downwards ...
53 views

### No friction in pure rolling - how about driving a car?

I remember the un-intuitive result that pure rolling without acceleration involves no friction by the law of conservation of angular momentum. Conjectures: I understand that when I'm driving a car at ...
63 views

### Thrust needed from an engine to reach orbit

Assume you had an airplane with magical engines that didn't need fuel, air or power, to operate. What thrust to ground weight ratio would the airplane need to reach orbit? By ground weight I mean mass ...
151 views

### Why are golf balls the only (famous) object with dimples?

To my knowledge there isn't anything that uses dimples to reduce drag. It's weird to hear why dimples are useful and help the ball go farther while at the same time finding no other examples. I ...
223 views

### Did Usain Bolt really sustain 11 horsepower of exerted power during the 100 m sprint?

I've just come across a WP article which says: "The Jamaican sprinter Usain Bolt produced a maximum of 3.5 hp (2.6 kW) 0.89 seconds into his 9.58 second 100-metre (109.4 yd) dash" Out of curiosity, I ...
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### Which way would objects, inside a container falling through earth's atmosphere, move, relative to the container?

Say, a sealed hollow container with 1 atm air pressure inside, is falling through earth's atmosphere. It is falling steadily with one side always facing the ground (Front Side) Inside the container, ...
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### Aerodynamic Force Decomposition

We know that aerodynamic drag is proportional to the square of the velocity of the incoming flow: $$D=kV^2.$$ If I decompose velocity into arbitrary orthogonal $x$-$y$ directions:V_x=V\cos\theta\\...
167 views

### With drag, why does it take longer for an object thrown upwards to fall back down than it does for it to reach its highest point? [duplicate]

Why does it take longer for an object thrown upwards to fall back down than it does for it to reach its highest point? We can draw a free body diagram for when the object is falling down and for when ...
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### How to calculate air resistance? [closed]

What is the best way to calculate or take into account air resistance? I have an assignment which goes as: Drop an object by itself and with a parachute, calculate air resistance for the parachute. ...
26 views

### Does the Choice of Coordinate System Matter for a Particle Falling Downwards in a Linear Medium

I have a question regarding John Taylor's treatment of a particle falling down in a medium that exerts a linear drag force (Chapter 2 of his book "Classical Mechanics").First some background, he ...
594 views

### What is the reason terminal velocity changes with radius?

I know that terminal velocity equals to some multiple of radius square. What is the physics behind this relationship. Is it just because as terminal velocity increases, the surface area increases and ...
28 views

### fluid flow over a incline and decline slope

I was recently watching fluid flow simulations on a cone. And noticed that if the tip on the cone is facing in the opposite direction to the fluid flow i.e fluid flow in $+x$ and tip of cone in $-x$ ...
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### Can pressure drag ever have a linear relationship?

I know from aerodynamics that pressure drag has a quadratic relationship for high Reynolds number of $10^4$ but what if the Reynolds number is between 1 and 10^3 say can pressure drag have a linear ...
39 views

### How to calculate drag caused by string?

An example - I throw a tennis ball with a short string hanging off one side. As the ball flies the string is dragged to the side opposite the direction of the ball's velocity vector, anchoring the ...
30 views

### Small amplitudes and Stokes drag law

Why is it that on a damped harmonic oscillator or a pendulum in a fluid, the Stokes drag law in the fluid only applied to small amplitude oscillation compared to large amplitudes oscillations? Dose ...
17 views

### The effect of mass on the optimum angle of a projectile, taking into account air resistance

I know that air resistance causes projectiles to have an optimum angle that is below 45 degrees, however, when we compare projectiles of different masses, for example a golf ball and a ping pong ball, ...
38 views

### Does dark matter experience drag?

Is dark matter dragged around the galaxy by gravity as stars and groups of stars orbit the galaxy, and, if so, is its shape/distribution deformed? Similarly, would the Oort cloud be deformed by being ...
31 views

### gravitation (kinetic energy and angular momentum)

When a satellite in a circular orbit around the earth enters the atmospheric region it encounters small air resistance to its motion. then (1) kinetic energy increases (2) angular momentum decreases ...
56 views

### Why are there no coefficients of drag for cubes and cones of low Reynolds numbers

I am currently reading ''Fluid Mechanics-Fundamentals and Applications'' by Yunus A.Cengel and John M.Cimbala. I am currently reading about drag coefficients in chapter 11 and how it talks about the ...
46 views

### Resistance in fluids

Is atmosphere depth important in reaching terminal velocity in terms of slowing down an object. For instance, if a meteor was dropped from height $h_1$, would it hit the ground with the same velocity ...
49 views

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

I'm in need of a equation that can tell me how much energy/work I need to move an object inside a low air-pressure tube. The equation should (if possible) include drag, object velocity and mass. If ...
23 views

### 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 ...
50 views

### 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 ...
67 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 ...
### 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 $60 m/s$ ...