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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Optimum baseball distance from velocity
I am trying to come up with an equation that is able to approximate the magnitude of velocity of a baseball after it travelled a certain distance in the $x-$direction given the ball is thrown at an ...
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Unreasonable values obtained for a simplified helicopter in equilibrium
I'm attempting to analyse a simple model of a helicopter. For one of my equations, I'm summing the forces in the x direction (forward motion). There are only really two forces acting on the helicopter,...
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Would an adhesive surface have more air resistance?
Imagine spreading double-sticky tape all over the surface of a car or a plane. Would there more significantly more aerodynamic drag as a result of the adhesive 'sticking' to air molecules and slowing ...
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Shooting a bullet in motion
If a bullet is shot from a firearm from a moving car in the direction of movement, would the speed gained with respect to the car be same as the speed of a bullet that is shot from an immobile gun?
I’...
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What causes drag crisis?
While reading the Wikipedia article on Drag Crisis, I found:
The drag crisis is associated with a transition from laminar to
turbulent boundary layer flow adjacent to the object.
While, the ...
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Lift and drag forces in parachuting
EDIT: guys, I am not a physicist and it is not my study field, So even if you see my question is silly to be answered, I hope you can give me a clue.
I hope you are doing well.
I have some questions, ...
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Is the sensation of falling purely due to air resistance?
When I jump off of something, even with eyes closed I can be pretty certain that I'm falling due to the associated sensation of falling. However, as gravity should be affecting each of my internal ...
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Showing that the integral giving the total induced drag exists
In John Anderson's Fundamentals of Aerodynamics the following expression for the total induced drag is given on page 442
$$D_i = \rho_\infty V_\infty \int_{-\frac{b}{2}}^{\frac{b}{2}}\Gamma(y)\alpha_i(...
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Why is it faster to swim under water than on the surface?
In competitive swimming, swimmers are allowed to swim first 15 meters completely submerged, and it seems that they can swim much faster that way than if they swim on the surface.
I've seen several ...
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How to calculate the drag of inclined object?
For example, we have inclined flat panel in the plane that is parallel to the wind:
We can split the velocity into V1 = V * sin(α) and V2=V * cos(α)
then calculate two Re numbers and two Cd ...
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Need help solving a projectile motion problem: finding the angle for a thrown ball to intersect with a vertically falling ball
The problem states that a ball is dropped from rest and falls under the influence of gravity (neglecting air resistance). At the same time, another ball is thrown with an initial velocity of v0 from a ...
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Does a cast net close as it descends or maintain shape?
There has been a bit of conjecture that fishermen's cast net closes gradually as it descends into the water column on the way to the bottom. My way of thinking is that a parachute stays open, despite ...
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How to decompose Plasma ion Drag Force on a particle moving through it?
Almost all papers on plasma mentioned that plasma ions drag on a particle is in the direction is opposite to the velocity of the particle. But no one said anything about the other two components; are ...
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What are the Components of drag force in spherical polar coordinates? [closed]
How to decompose the drag force in three components of spherical polar coordinates?
Since
$ F =\frac{1}{2}\rho C A v^2 $
or in vector form :
$\vec F = \vert F\vert \hat F = \frac{1}{2}\rho C A v^2 \...
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Effect of apex vent on reference area in equation for drag coefficient
I am trying to investigate the effect of apex vent (vent ratio) on the drag coefficient of circular parachutes, via a drop test using scaled down parachutes. How do I determine the reference area of ...
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Cyclist coasting on a plane road (only air resistance and rolling resistance apply)
I am currently trying to simulate a cyclist. Right now I am looking at the change of velocity when the cyclist is coasting on a plane road. These are the values I am using:
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Air resistance in two dimensions
Suppose I have a ball moving through the air parallel to the ground, and diagonally in some 2D $x$ , $y$ coordinates (along the line $y=x$). Let's say its velocity is 1 units, which means on the $x$ ...
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Power consumption / energy expenditure to maintain constant velocity while riding a bicycle at $1\times$ velocity vs $2\times$ velocity
Consider the case of someone riding a bicycle on an even horizontal surface at a constant velocity. As they are riding at a constant velocity, there is presumably a constant energy expenditure (which ...
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How can you tell that the aerofoil has an asymmetric section only by looking at Lift to drag ratio against AOA?
I am new to aeronautics and I am interested to know how can the section of an aerofoil be determined just by looking at its lift-to-drag ratio against angle of attack ( $C_l/C_d$ as a function of AOA)....
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How can I estimate the drag of a CAD model?
I have a CAD model that I’m trying to optimize for hydrodynamic-ness, programmatically (preferably with Python).
Is there a way I can find or estimate the drag force of the model, without having the ...
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Integrating both sides of an equation w.r.t. two different variables ($dz$ and $dv$)
so I'm trying to derive an equation for the maximum height an object reaches after being vertically thrown upwards, where the two forces acting on it are gravity and quadratic air resistance, so that
$...
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Why is a viscous drag produced due to relative motion of layers of fluids? [closed]
When two layers of fluids move over each other, a viscous drag is produced. Could you please elaborate on this?
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Is air drag approximately the same on both a smooth ball and a tennis ball?
I am writing a project about projectile motion in 2D at a high school level to the point where I only know the simple drag equation. The experiment I did was firing a tennis ball with a compressed ...
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Regarding Speed of launched rocket inside the atmosphere
I am a 15 yr old, so please forgive my mistakes as I have not entirely read rocket mechanics.
I have been wondering why rockets accelerate to mind-boggling speeds, (mach7-8 or even more)when that must ...
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Can the damping coefficient of a pendulum be predicted given physical variables?
I'm aware you're able to calculate the coefficient of damping, $b$, given a set of amplitudes over time through $$\ln(\theta/\theta_0) = -bt/2$$ However, is there any way to get $b$ without empirical ...
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Drag force on a bicyclist
Recently, I wrote an introductory physics exam where I encountered the following problem:
We look at a bicyclist with the wind drag force $\vec{F_R}(t) = -k \vec{v}(t) |\vec{v}(t)|$ who accelerates ...
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Husband and Wife with Metal and Fabric Parachutes [closed]
Let's suppose: an open parachute made of fabric with a lady hanging below, starting from stand still, falls from 5000 meters. Another parachute made of thick metal, with the same size and shape as the ...
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Speed of objects travelling down liquid-filled tubes of different widths
Consider I have two tubes filled with water: Tube A and Tube B. Tube A has a diameter of 20mm and Tube B has a diameter of 10mm. A marble ball with a diameter 8mm is dropped down both tubes.
Why does ...
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How damping constant of pendulum varies with length of wire? (experiment result confusion)
I'm a high school student doing an experiment for my physics course. The experiment aims to find out the relationship between the damping constant and the length of the wire. The constant is ...
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The case of an initial velocity greater than final velocity with a drag force proportional to the velocity squared
consider an object with a mass $m$ falling in a fluid with a drag force proportional to its velocity squared $(f=kv^2)$.
the governing differential equation can be found using Newton's second law of ...
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Is the drag coefficient same for two object with same shape, same size (radius) and same outer material but different mass?
I am doing an experiment where I want to measure the effect of the change of mass of the object to the terminal velocity of the object when falling down a liquid.
I am using a ping pong ball and I ...
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PI controller - output calculation [closed]
The propeller of an airship is connected to a DC motor. The motor is being controlled using a PI controller. The PI controller has a proportional gain of Kp = 2, and an integral gain of Ki = 0.5, and ...
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What is wrong with my drag equation? [closed]
I'm working on the equations of motion for a coupled pendulum. Its still a rough draft. My problem is with the drag force. Is there an instance where the "l" should be squared first? and if ...
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Do objects always speed up as they fall? [closed]
In the thermodynamics video I watched, it was stated that objects at higher elevations have more energy. And that objects must speed up as they fall. My question is, "what happens if an object ...
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How to solve the trajectory equation using quadratic drag formula?
I am doing a project on ballistics and projectiles and I was reading this link here and it states that the ballistics equation cannot be integrated analytically, and has to be integrated numerically. ...
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How can an airfoil create more lift than drag?
According to law of conservation of energy, energy can only be converted, not created.
Airfoils convert airspeed to lift, or to put it differently, they create a positive lift force by creating a ...
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How to develop a high drag surface geometry to have a desired relationship with the angle of rotation?
Similar to the functioning of grid fins(used in missiles and rockets), I need to develop a high drag structure for speeds less than 30 m/s, these structures will have a similar rotation lines to that ...
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Attempting to Model Air Resistance in Javelin Flight
I am trying to do a mathematical modelling project on javelin flight and correlate the data to real life data from the Olympics. Obviously, drag is an important component of the flight characteristics....
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Have multiple terminal velocities for a rigid body ever been verified experimentally?
The coefficient of drag can drop suddenly for some objects at high Reynolds numbers. If the drop is "fast enough" then the total drag force, $F=1/2 \rho A v^2 c_d$, could actually drop. This ...
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Is This Derivation of Velocity as a Function of the Force of Air Resistance Correct? [closed]
I have seen the derivation of velocity with air resistance done using the equation, $F_d=-bv$ where velocity can be expressed as
$$v(t)=v_0e^{-\frac{b}{m}t}.$$
However, I'm looking for a corresponding ...
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Friction and Lenz's law
A professor asked, in an interview, about the microscopic interpretation of friction, and whether we could think up a reasonable (without getting too quantitative) model for it. From the buildup ...
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How is the damping coefficient $b$ calculated for the air resistance for a sphere (horizontal motion)?
The derivation of velocity which takes air resistance into account takes the form:
$$v=v_0e^{-\frac{b}{m}t}$$
which is derived from $F_D=-bv\implies a=\frac{F_D}{m}=-\frac{bv}{m}$. I heard that the ...
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How is momentum conserved when dealing with viscous substances?
Say we drop a ball into a bucket of honey. The falling ball will have a downwards momentum, but once falls into the honey, it will slow and then stop with no apparent opposite momentum. In such a case,...
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What is the difference between drag coefficient and skin friction coefficient?
I am trying to understand what caused drag. For example when fluid is passing a plate, if the fluid is still laminar at the end of plate, the drag coefficient could be evaluated as twice friction ...
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What is the hydrodynamic interaction (Oseen kernel)?
I am reading through the paper "Dynamics of Membranes Driven by Actin Polymerization" by Nir S. Gov and Ajay Gopinathan. In this paper, the authors develop a PDE model to explore the ...
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Calculating the angle an object has to be launched at with simulated drag [closed]
I’m trying to calculate the angle(s) a projectile has to be launched at in a game that has a simulated drag which reduces the velocity by 2.5% of the current velocity per tick (25 milliseconds). This ...
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Why does static friction opposes force vector ...but kinetic friction opposes velocity vector?
MY ANSWER- lets say a body is on rest and a force is applied thats slowly increasing ....the tiny bumps and groves between surfaces will apply a normal until the force is big enough to break through .....
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A curveball in vacuum
So I’m still new to physics so forgive me if it’s a simple question. Assume no air resistance. Suppose I throw a curveball at 30 m/s at an angle of 10$^\circ$ from the horizontal. Assuming I’m not ...
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Is it possible to convert separated flow back to attached?
Sometimes you cannot easily create ideal single streamlined shape...
Would it be possible to attach separated flow again somehow?
The point is - you have some base setup (average cyclist) and want to ...
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Brachistochrone problem with drag
If we didn't consider friction, this would just be the brachistochrone curve. But what would the optimal path be if there was also a drag force that was in proportion to the object's speed?
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