Drag Definition and 713 Threads

Homework Statement Write down the equation of motion for the downward journey of a baseball subject to quadratic drag. Find v as a function of y and, given that the downward journey starts at ymax (given below), show that the speed when the ball returns to the ground is: vterv0 /...

Basically..I have a canon that shoots a pingpong ball at 30m/s from any angle between 0-90 I've derived all my equations as can be seen below: So the velocity equations are: Vx(t) = (Vxo)e^(-kt/m) Vy(t) = (Vyo+gm/k)e^(-kt/m) − gm/k Integrate these to get X and Y as functions of...

I am trying to experimentally derive the drag equation. I have dropped coffee filters with varying masses and determined their resulting terminal velocity. I plotted the data and found that the mass of the coffee filter is proportional to the terminal velocity squared. I was now wondering how I...

Can someone please explain the lift coefficient and drag coefficient in simple terms? Thanks.

Facing some horrible mathematical situation while solving to find equation of trajectory of projectile when drag is proportional to v^2. my equations where i end up with are as follow: equation 1: mdv/dt=(-kv^2)+(-mgsinγ); equation 2: (-mv)dγ/dt=mgcosγ; equation 3: dx/dt=vcosγ; equation...

How does the flap angle affect lift to drag ratio of a wing?

I am trying to measure the lift to drag ratio of a wing. I am measuring the lift by using a electronic scale. But how on Earth can I measure the drag force?

Homework Statement So i am trying to find the maximum power transfer of a circuit. See attached image. Is there any way to automatically drag the cursor of a plot to the maximum/minimum amplitude of a signal when simulating LTspice? Or do you need to manually drag the cursor and estimate values...

Homework Statement A particle of mass m is thrown upward with velocity v and there is retarding air resistance proportional to the square of the velocity with proportionality constant k. if the particle attains a maximum height after time t, and g is the gravitational acceleration, what is...

Homework Statement Hi, I am doing a theoretical investigation which will be compared to an experimental I'll do later. I am trying to calculate how much time will it take an object to fall a heigh H. the object is a 5x5x5 cm cube. I have the Reynolds number as this Re=3546*Velocity; and I...

Hi I'm trying to model the drag effects in using Lagrange Mechanics and trying to include the effects of aerodynamic drag. I've read up on the Rayleigh Dissipation functions in Greenwood's "Advanced Dynamics" and a few other books but they always provide the Rayleigh function for drag forces...

Hello everyone, I have a question regarding the accumulated drag curve shown in the figure below for the CFD simulation of external flow over an automobile. (It is written Vehicle Cd in the figure) It can be seen in several regions that the accumulated drag curve is dropping (ie., having a...

Hello everyone, I have a question regarding the accumulated drag curve shown in the figure below for the CFD simulation of external flow over an automobile. (It is written Vehicle Cd in the figure) It can be seen in several regions that the accumulated drag curve is dropping (ie., having a...

I have a drag car I'm wanting to do some testing on . Would anyone mind giving me some insight. A Pm or on here is fine. thanks.

I'm trying to calculate the aerodynamic forces on a flat plate as a function of angle of attack. The drag force is calculated from F = ρ*V^2*A*Cd/2 Where ρ is the air density, V is the wind velocity, A is the area, and Cd is the drag constant. Simple question: For A, should I use...

Dear Experts, I am 4th year undergraduate who did experiments for drag reduction in swim cap. I had applied hydrophobic and hydrophilic coatings on my cap. My final results are shown in attachment below. The no cap has more drag than body with swim cap without coatings. There is not much...

Hi, I've read in a website that the drag (air resistance) formula for a car would be different: -> for velocities under 86 km/h Drag = K(coefficient) * V -> for velocities over 86 km/h and under 1200 km/h Drag = K(coefficient) * V^2 I've researched a little bit and only one...

Homework Statement A skydiver drops o¤ an outcrop at the top of a sheer face on a mountain and falls vertically downwards. Let v(x) be the velocity of the skydiver at a vertical distance x below the drop-off point. As the skydiver falls he will experience a drag force of magnitude...

Lift and Drag...Which frame of reference? Hi, When expressing the Lift and Drag acting on an airplane as: F_{lift}=qSC_L F_{drag}=qSC_D where q is the dynamic pressure, S is the wing ref. area, and C's are the lift and drag coefficient. My question: Some sources, like this one...

Could someone explain to me the difference in calculating the coefficient of drag with thrust, and without. What causes the difference in application?

Homework Statement At international cricket games, it is commonplace to display on the scoreboard a speed for each bowl. Because the ball is subject to a drag force due to air proportional to the square of its speed given by R = kmv^2, it slows as it travels 20 m toward the wicket according...

Homework Statement An object moving in a liquid experiences a linear drag force: D⃗ =(bv, direction opposite the motion), where b is a constant called the drag coefficient. For a sphere of radius R, the drag constant can be computed as b=6πηR, where η is the viscosity of the liquid. Find an...

A sphere, 14.7 mm in diameter, drops at a rate of 0.08 m/s in oil µ = 0.1 Ns/m^2 , σ = 0.85 ). Calculate the drag force acting on the sphere. [Answer: 1.85e-3 N] F_d=0.5*rho*C_d*A*u^2, Re=u*p*L/μ I attempted to find the Re, but am struggling on finding the coefficient of drag...

I need to calculate the increase in drag due to an airbrake, however the formula includes "semi span". I'm unsure if this is simply wing span/2 or is it the length of a wing in which case it would be (wing span - fuse width)/2. Any help would be good.

I am designing a test rig for my company to test seals. What i have is a shaft spinning in a fluid column that is pressurized to 30 bar. The shaft is spun by a motor and i am currently trying to figure out what motor i should select. The fluid is a C4 SAE 30 Oil, quite viscous actually. My...

Homework Statement mass = 100 Kg Cross Area = 4 Drag = .4 Initial velocity = 17.59 m/s Gravity = 9.81 Angle Changes according to the position of the mouse Terminal velocity = 31.649 ; Don't know if its relevant but I calculated this Homework Equations Y1 :=...

Homework Statement Hi, i have a peculiar question after watching MIT lecture:http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-12/ What is the difference between the equation representing the drag force for a sphere...

Hi Is the drag coefficient for a particular object the same in different mediums? Say we have Cd = 1 in air for one object, is Cd the same for this object in water?

My classical mechanics textbook says that, for a projectile, the linear drag force is given by f = -bv and the second law is written as m\ddot{r} = mg - bv (a second order differential equation) which can be rewritten as m\dot{v} = mg - bv (a first order differential equation) because the forces...

For several years i have thought about air (fluid) resistance without getting deeper into the formulas that model its behaviour. Recently, I've decided to take one more step in the subject and learn some of these formulas. I've learned about the drag equation, and at first glance it seemed...

I'm no engineer, but just a pilot trying to estimate the drag of my small two-place airplane from the relevant formulae. My plane is quite draggy, and from comparison with other aircraft data, I have taken Cd,0 as 0.043. Apart from this, I calculate the induced drag at a given speed from the...

Dear Experts, I really need help with the calculation of virtual mass and drag of an object. Firstly, I am doing final year project called Drag reduction in swim cap. Before I go into using swim cap. I am try to measure the drag using accelerometer that inside a bottle but I am damn...

As you can see, around Reynolds number of 5 105 the transition occurs for a smooth sphere. However, why is it that after this transition that the drag coefficient increases at turbulence?

Homework Statement How does Bernoulli's Equation for calculating the pressure in a moving fluid (as below) explain that drag increases proportionally to the square of the speed? I have been dropping parachutes and recording the time to fall, so my question is in reference to free-fall motion...

My issue/knowledge Hello all, I think this is my first time posting a question here (I have read the guidelines). This problem is not in my textbook or notes, and I'm not sure how to go about it. Online all I can find about air drag equations requires knowing variables which I'm not given here...

Hi, this is my first time posting on this forum. This is a question about how to approach questions about one-dimensional motion with drag. A link to the question: http://puu.sh/5fOCO.png While attempting this question, I thought the two equations they were referring to were: dy/dt = v...

Hello, I was reading somewhere about how to control Rudders in RC planes. The basic equation here is the drag equation: F=0.5*ρ*v^2*C*A (take ρ=1Kg/m3) where v is the velocity, C is the Drag coefficient of the control surface (Rudder in this case) and A is the area. I am wondering if we have...

Hello, I just want to make sure I am doing this right. As an example, if I want to add a spoiler or hood scoop to a car, after I find the correct coefficients of drag, can I assume that the total drag force acting on the car is ƩFD=drag of the car + drag of the spoiler+ drag of scoop, etc...

Hi, I know that the drag force on an object: Fd= 1/2 . ρ . v^2 . Cd . A where A is the reference area. But in the case of a streamlined body, I don't know what will be taken as the reference area. Should it be the largest cross-sectional area of the body?

Homework Statement We are given 3 coffee filters. Using a stopwatch and a meter stick, make measurements to predict how long it would take for those filters to fall down a stairwell. Come up with an experimental method to predict this time. During the lab, we will be told the number of...

I have a question but it's not so much a specific HW problem as it is with trying to conceptualize the physics behind it. So when dealing with aerodynamics, let's take for example a wing / airfoil. I understand due to a difference in pressure lift is generated. Higher pressure wants to...

Why is it important to ensure flow separation does not occur in the back of a vehicle or wing? I know that when flow separation occurs its when you have a large differential pressure which in turn cause turbulence and drag. I understand that with more drag you have less efficiency. But if...

Here is the question: I have posted a link to this topic so the OP can see my work.

i have an object thrown up in the air with drag present. i want to know how much time it takes to reach the peak ie when v=0 m\ddot{x}=-mg-kv2 basically, i don't know which one to use for drag, I've seen bv being used before in problems, and I've also seen kv2 being used before in...

Homework Statement An object moving in a liquid experiences a linear drag force: D⃗ =(bv, direction opposite the motion), where b is a constant called the drag coefficient. For a sphere of radius R, the drag constant can be computed as b=6πηR, where η is the viscosity of the liquid...

Lately, I have conducted an experiment where I dragged various circular cylinders through water in order to find the resistance, and hopefully also the drag coefficient. It seems to me that this coefficient is dependent on what is called the Reynolds number. Using some sources, I can easily find...

Here is the question: I have posted a link there to this topic so the OP can see my work.

Okay, so the scenario is a passenger car, traveling on the highway. As a general rule, I say that increased weight (mass) will have a beneficial effect on MPG (IF tire pressure is increased so that rolling resistance is reduced to compensate for the increased weight), ONCE the vehicle is up to...

Homework Statement This problem is from a homework assignment. The professor says that the the ping-pong ball will go up if the cd = 0 and will go down if the cd is much larger than one. Is this logic correct? I keep thinking about how if an aerodynamic car is pushed by wind, the car...

Hello All, Homework Statement I was at the firing range the other day when the gun instructor mentioned that the bullet of a AR-15 rifle can travel 5 - 6 miles depending on the angle of the gun when the bullet leaves the muzzle. I wanted to confirm this for myself so, I tried to find the...