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.

112 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
7
votes
3answers
1k views

Drag - Dimensional Analysis / Buckingham $\pi$

I'm working on dimensional analysis and I'm having trouble. Here's a problem from my book I'm working on. I'm supposed to consider a small sphere experiencing acceleration due to gravity $g$. The ...
4
votes
1answer
561 views

Variables in calculation of drag coefficient

Okay, so I looked up drag force equation, and I found that the equation involved the drag coefficient. Then I looked up the drag coefficient, and the equation for it involved the drag force. ...
3
votes
0answers
319 views

Torque due to air resistance on a frisbee

In my analytical mechanics course we worked out an example involving a disk (say, a frisbee) rotating after being thrown into the air. The disk experiences a torque proportional to its angular ...
3
votes
3answers
2k views

Projectile, air resistance and wind

So for my school project I am working on a projectile simulator and air resistance. So I have looked at this. Equations for an object moving linearly but with air resistance taken into account? ...
3
votes
1answer
489 views

Explaining the shape of a raindrop and a drop of mercury

I saw on wikipedia that the shape of a raindrop is explained by using Laplace pressure. But why? Since the drop is in motion, we shouldn't be able to use an hydrostatic law, am I wrong? The ...
2
votes
1answer
90 views

Determine initial velocity of an object which was thrown (WITH air resistance)

I have the following problem: I want to determine the initial velocity of an object which is for example dropped from a moving plane. I know the position, from where the object is dropped and I know ...
2
votes
1answer
90 views

Aeronautical Physics induced drag direction

I am a 9th grader doing a science fair project at my local high school. I am doing a science experiment on different plane wings and how the angle of attack affects drag. I need to create a rig to ...
2
votes
0answers
456 views

What is wrong with this downforce calculcation?

I tried calculating the downforce of a spoiler I need for a robot. I used this formula. $$F = \frac{1}{2}Ac_a\rho v^2$$ Where $\rho$ is air density, $v$ is the speed of my robot, $c_a$ is the lift ...
2
votes
0answers
576 views

Why did increasing the Ackermann geometry in my race car make it faster in corners?

Ackermann geometry is used to account for the different radius arcs that the front tires follow when the steering wheel is turned from center. It's often expressed as a percentage: e.g. 25% Ackermann, ...
2
votes
1answer
830 views

What is the drag coefficient of an open wedge?

To check my two dimensional CFD calculation I am looking for reference data on the drag coefficient of an open wedge. The geometry is shown below, together with the flow direction. I have found ...
1
vote
0answers
39 views

Friction at high speeds

I am reading a book which mentions that frictional force is not exactly proportional to the normal force at high speeds. Quoting: Once the bodies slip on each other frictional force is, $kN$. This ...
1
vote
1answer
31 views

Calculate the kinetic friction velocity vector from the kinetic friction force in a simulation

I am doing (programming) a simple kinematic 2D simulation on blocks. The idea is that the block will have a force applied. 1) From the force and mass I calculate the the acceleration vector (will ...
1
vote
0answers
21 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 ...
1
vote
0answers
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 ...
1
vote
0answers
58 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 ...
1
vote
0answers
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 ...
1
vote
0answers
38 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 ...
1
vote
0answers
43 views

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 ...
1
vote
0answers
34 views

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 ...
1
vote
2answers
106 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 ...
1
vote
0answers
41 views

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 ...
1
vote
2answers
45 views

air pressure to assist lift on a Race boat

We have a 25 ft race hull with Jet drive pump (we race 30+ mile legs), we are hitting sppeds @150mph. lowering the hydronic drag is a challenge, i am thinking about installing a air injection system ...
1
vote
1answer
60 views

Linear motion equation with intital velocity and water drag

at the start i want to mention that i am from germany, so my english is not the best! For a boat simultaion project i am working linear motion equation with intital velocity and water drag. For ...
1
vote
0answers
250 views

Emperically Determining Terminal Velocity of a Sphere Falling over Critical Mach Number

I originally thought that the terminal velocity of a smooth sphere in free fall through the atmosphere would be an easy question to answer. But for heavy spheres of small diameter, the terminal ...
1
vote
0answers
25 views

Are the end velocities of masses (falling from infinity to earth) with equal $\rho$ and arbitrary form , scale independent?

Yesterday I asked a question I didn't intend to ask. Of course, masses with different forms (and equal $\rho$) do not reach the same end velocity when falling on earth from infinity. What I meant to ...
1
vote
0answers
81 views

How to calculate lift and drag of a non-standard aerodynamic body

It is my understanding that the standard method to calculate the lift and drag characteristics of an airfoil is to use formulae and existing data of its coefficients of lift ($C_l$) and drag ($C_d$). ...
1
vote
0answers
116 views

Trajectory Required to Hit Target with Newtonian Drag

I'm trying to write a function to determine the trajectory angle of a projectile, theta, from the horizontal required to hit a specified target location. Inputs: ...
1
vote
0answers
122 views

Effect of atmospheric drag on earth's rotation

Okay, so I had a question answered regarding the earth rotating and planes flying east and west but one part of the answer talked about how the atmosphere is moving along with the earth (same angular ...
1
vote
0answers
34 views

Feasiblity of a long spinning top using an electromagnet to pull on Earth's magnetic field

Would it be feasible to build a infinitely spinning top (ref. Inception) by including a battery powered electromagnet who's polarity flipped in sync with the top's rotation such that the pull against ...
1
vote
0answers
239 views

Calculate ballistics using Pejsa method (bullet physics)

I'm not sure if it was already asked, but, could someone please explain the Pejsa method of ballistics, specifically the velocity and trajectory (no energy, wind or lead etc.) (just drop drift and ...
1
vote
0answers
450 views

Drag Force on a cylinder with its long axis aligned with the flow

yesterday I started looking into equations that link a cylinders diameter $r$ and length $L$ to the force experienced in a highly viscous medium ($Re<<1$). I found the onseen-approximation but ...
1
vote
0answers
115 views

Approximation for rotational drag on a box?

The drag equation gives us an approximation for the drag on an object caused by its velocity in a fluid: $F = \frac{1}{2} \rho A v^2 C_d$ Is there any similar approximation for the rotational drag ...
1
vote
2answers
72 views

What are the major differences in group-skydiving as opposed to “single” skydiving?

Surface area/the cross-sectional area is greatly increased, so my thinking is it should decrease terminal velocity as well as a couple of other factors. But mass changes too (since there would be more ...
1
vote
0answers
121 views

Wind resistance on moving body

Suppose that a vehicle is traveling 60 km/h north, and the wind speed is also 60 km/h going the same direction, would there be wind resistance, and to what extent? Also, if I put my hand outside the ...
1
vote
0answers
591 views

Max speed as a function of engine power

My question started out as finding the maximum speed of a go kart, taking into account only the drag forces as force opposing the motor. I've done some investigation to find: $$ F_{drag}=\; \frac{\...
1
vote
0answers
301 views

Finding Time & Required Angle for Projectile Motion with Quadratic Air Resistance

This is a physics/calculus/computer science problem, but I think I'll get better results in the Physics SE. I have a fun little project I've been working on (hobby, not homework/production), that ...
0
votes
0answers
27 views

How can I find the initial velocity of a projectile from its range, when accounting for air resistance?

I'm trying to find the initial velocity of a projectile based on it's range. I know how to use kinematic equations to do this when air resistance is ignored, but I'm not sure how to take into account ...
0
votes
0answers
18 views

Drag force on the thin string loop rotating in air

I'm trying to figure out what is the drag force per unit of length on the circular string loop rotating in air around its symmetry axis. In particular I'm interested how this force depends on the ...
0
votes
1answer
43 views

Why do we consider the viscous force to be tangential?

Is it that since it is a friction force, it needs to be tangential as other friction forces like kinetic friction and static friction forces are?
0
votes
1answer
43 views

Finding displacement by integrating forces that vary with velocity

I have a body that is being affected by forces, some of which are invariant ($F_i$) and some of which vary with velocity ($F_v(v)$). Given that $F=ma$ (where $F=F_i+F_v(v)$), how do I integrate this ...
0
votes
0answers
26 views

Drag force as a function of shear & normal stresses

I would like to understand the relationship between the drag force of an object in a fluid and the microscopic interactions between the object and the fluid particles. Specifically, I would like to ...
0
votes
1answer
29 views

What's the “cause” of damping coeff. in springs?

What's the "cause" of damping coeff. in springs? Air resistance, friction?
0
votes
2answers
60 views

Flight time of spherical bullet fired horizontally versus dropped vertically / effect of crosswind on spherical car

Would a spherical bullet fired horizontally from a musket stay aloft longer than a spherical bullet dropped from the same height? I know two similar questions have been asked (Will a bullet dropped ...
0
votes
0answers
32 views

Davis formula application

So I stumbled upon the Davis formula for trains while doing some researches about my project but I don't know how to apply it (programmatically) : Let's say for example this variant : $$R'=1.3+\frac{...
0
votes
0answers
35 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 ...
0
votes
0answers
33 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 ...
0
votes
0answers
44 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 ...
0
votes
0answers
66 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 ...
0
votes
0answers
78 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 ...
0
votes
0answers
46 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 ...