Drag Definition and 751 Threads

Homework Statement A drag racer, starting from rest, accelerates to ¼ mile with a constant acceleration whose magnitude is 12.427 m/s2. At the end of the ¼ mile, a parachute opens, slowing the car down and bringing the car to a stop after 40 seconds. From the time the parachute opened, how...

Drag at high Reynolds numbers is given by the formula: 0.5*\rho*V2*Cd*A Why does at the molecular (or at the micro) level the drag is independent of the viscosity?

hello! i'm doing a physics lab paper helicopters and changing the length of their wings. i was wondering if i could find the coefficient of drag for each helicopter. i have the mass of the helicopter, the time it takes to fall a certain distance and I'm assuming that the cross sectional area...

Homework Statement Drag=m(Mu*g+(V^2)/L) L=constant with unit of length initialV=V_0 how far the car will coast under this condition with initial V how long does it take to stop Homework Equations a=V*dv/dt The Attempt at a Solution there are linear and non-linear parts in this...

For fun, I wanted to crate a program that dealt with 2d projectile motion w/ wind resistance. Specifically, where the object started from rest at a given height. I looked up several equations that dealt with wind resistance. Specifically, drag force. Drag force was defined as Fd = CdPAV^2/2. So...

Homework Statement A particle of mass m and electric charge q>0 is subject to a uniform, constant mag field of \vec{B} = B \hat{k}. At t=0 its velocity vector is \hat{v}naught which lies in the x-y plane. The particle is also subject to a linear drag force fd=-b\vec{v} a)Draw a free body...

Homework Statement This is a small part of a problem I'm getting stuck on. I'm going to skip past the beginning steps to a part that I know is correct before I get stuck. We have a baseball thrown up into the air, with quadratic drag. I'm attempting to solve for an equation of motion y(v)...

I'm kind of stuck in my search, hoped to be able to find some answers on this board. Anyways, I've been taksed to design a slow speed mixer and I'm trying to look up information beyond Stokes Law of FD = 6 pi r V u The fluid to be mixed is approx. 100000 poise, incompressible fluid. I'm...

While I understand this is a basic question, I am a beginner with regard to fluid dynamics etc. To start, say you have a propulsion system capable of X Newtons and a weight of Y kg. I realize max speed occurs at the point at which the force of drag is equal to the force of acceleration, and the...

Homework Statement To demonstrate the tremendous acceleration of a top fuel drag racer, you attempt to run your car into the back of a dragster that is "burning out" at the red light before the start of a race. (Burning out means spinning the tires at high speed to heat the tread and make the...

Homework Statement How can I calculate the drag of different missile/torpedo shapes in water? I have five different shapes, similar cylinders with different "noses" One is a long cylinder with a flat nose, another is a cylinder of the same diameter with a hemisphere nose. Third and fourth...

Homework Statement Suppose a block sliding on a slippery horizontal surface experiences a drag force F=-cv3/2 where c is a positive constant. At time t=0, the block is at position x=0 with initial positive velocity. Find the velocity and position as a function of time. Derive an expression for...

I am going to make a R.C. airplane and need help understanding the physics behind it. I have found these formulas for lift and drag. Lift=Cl*(r*V^2)/2*A Cl=2*pi*AoA Drag=Cd*(r*V^2)/2*A Cd=Cd0+Cl^2/(pi*A*R*e) Now I have two questions. First, are these the correct formulas for finding...

Homework Statement I have to make a plot. This plot must illustrates a position of a ball, which is falling. My problem is that I don't know what v is in this equation. drag force= -C * ||v(t)|| * v Homework Equations To calculate the velocity: v(t+dt)=v(t)+a(t)*dt where t is time...

Homework Statement A projectile of mass 0.1 kg traveling horizontally through the air with speed v(t) experiences a drag force DT (t) whose magnitude is given by: D (t ) 0.001 [v (t )] 2 At one instant, the projectile’s speed is measured to be 100 m/s. Calculate the speed of the...

Hi, I am trying to caculate the aerodynamic drag on a weather balloon that's climbing through the atmosphere. Of course, the velocity is very low here, about 4m/s. Such a balloon is an almost perfect sphere. So I am trying to fill in the drag equation, but I still have two unknown...

Hello! First time poster, long time lurker. I've been doing my own independent study of fluid dynamics (not recommended, i know!) and I've hit a wall. I'm trying to imagine problems of fluid dynamics other than the "river and pipe" variety to confirm that I'm really getting this drag stuff. I'm...

Homework Statement I don't know if it's possible but I am doing a physics EEI on drag. I know to find drag you need instantaneous velocity which can be found through (change in x/ change in t) but i cannot find displacement unless i find velocity :S.. Homework Equations d = 0.5 x p x...

I working on a new airfoil design. Please tell me the airfoil having highest lift to drag ratio, I need it for comparison.

"A two-dimensional structure is tested in a wind tunnel with an air density of 1 kg/m3. The wind tunnel is 1 m high, with upstream and downstream pressures of 1.5 kPa gage (i.e. above atmospheric) and 1 kPa gage respectively. If the mean velocity of the entering air is 30 m/s and the downstream...

F = -kv2 A fishing boat of mass m moves through the water in the +x direction. At time = 0 and x=0 it shuts its engines off and begins to drift. It experiences drag according to the above equation, calculate the boat's speed as a function of time. I've tried taking F = ma so a = -kv2/m...

Homework Statement Air at 20kPa and 20°C flows across 5cm diameter cylinder at velocity of 20m/s. Compute the drag force exerted on the cylinderHomework Equations the formula should be use is this, FD = CD*A*den*V^2 / 2 where FD & CD is the drag force and drag coefficient, respectively The...

Homework Statement How large is the mass of sweat (water) evaporated by a man with 80 kg body weight assuming that his body temperature decreased due to the evaporation by 1 °C? (Assume, that the human body consists mostly of water and the heat of evaporation of water at body temperature (37...

x’’(t)=g-Fd/m=(9.81metres/sec^2)-(k/m)(x’(t)) where x''(t)=du/dt and x'(t)=u=dx/dt I enter this at http://www.wolframalpha.com/input/?i= and I get the solution x(t)= -(c1me^(-kt/m))/k+c2+9.81(m/k)t But x(t=0)=0 x’(t=0)=0 x(t=0)=c1+c2 x’(t=0)=c1-c2 =>c1=c2=0 =>x(t)=9.81(m/k)t and this...

Homework Statement The problem is Kibble & Berkshire 3.8, http://books.google.com/books?id=0a8dk0eDxgEC&lpg=PP1&ots=DT80qg1JSM&dq=kibble%20berkshire&pg=PA68#v=onepage&q&f=false" is a link. (The problem is on page 68. Equation 3.17, referred to in the problem, is on page 53.) I figured out the...

Hi everyone, this being my first post I will take this opportunity to say that you seem to have a very interesting forum going here! I have a question with regards the calculation of pressure drag over an aerofoil (or airfoil if you prefer). I am using a panel method coupled with an...

Homework Statement A golf ball and a basketball are both moving through the air at 10 m/s. Which has the higher drag coefficient? a. The golf ball's drag coefficient is much higher. b. The basketball's drag coefficient is much higher. c. Both drag coefficients are about the same...

Knowing the weight, the mass and the acceleration of the object, how can I find the drag force? I used the following formula --- "Weight – drag force = ma" --- but I'm not sure whether it is right or wrong. Mass = 0.14 Weight = 1.34 Acceleration = 8.63 1.34 – drag force = 0.14 x 8.63...

MAJOR EDIT: I fixed my position integral and got the answer to 1.ii) Homework Statement A parachutist jumps from a helicopter that's not moving. The mass of the person is 80kg, the quadratic drag is f = -Cv^2 where C = 3,52. Neglect the Earth's rotation effect. The parachute is opened as soon...

Hello all. I need to model the trajectory of a bullet fired from a gun while being subjected to gravity, drag, and a wind vector. It's been 10yrs since my last differential equations course and I can't remember much, except enough to think that they're required to solve this problem...

Homework Statement to qualify for a race a car must achieve an average speed of 254 km/hr on a track 1600 meters long. if a car covers half the track with an average speed of 227.5 km/hr what minimum average speed must it have the second half to qualify? Homework Equations...

Hi First ever post on Physics Forum. N2: F=ma can be written as dv/dx=-gy-(bv/m) g=grav. constant b=constant where D(total drag force opposing dir. of...

Homework Statement What is the drag force on a 1.6 m wide, 1.4 m high car traveling at 30 m/s (approx 65 mph)? Homework Equations drag force=.5*p*v^2*coefficient of drag*A The Attempt at a Solution density of air depends on temp but that's not given so I used a density of 1.2...

Hello PF'ers, I'm having a bit of conceptual trouble with understanding the drag force derivation. I take the drag force as being D \ = \ \frac{1}{4} \ A \ v^2 . I want to imagine dropping an object from the highest point at which the equation w = mg will be a satisfactory...

Homework Statement A block of mass m slides on a horizontal surface that's been lubricated with a heavy oil so that the block suffers a viscous resistance that varies as the 3/2 power of the speed. If the initial speed of the block is Vo at x=o, show that the block cannot travel further...

Homework Statement An aircraft is flying straight and level at 300 kilometers per hour at an altitude where the density is 0.9kg/m^3. The ratio of lift to drag coefficients for this aircraft at this flight condition is 15. Its weight at the moment under consideration is 98,000 Newtons. The...

HI i have been involved with a problem which requires me to calculate the drag of a finite circular cylinder of very low aspect ratio (~1.2) i.e the h/d= 1.2 The Red= 5.4x 105 (based on diameter) and the Rex = 8.46x 106 The flow regime is very low subsonic ( M=0.15) I need to predict the...

http://www.grc.nasa.gov/WWW/BGH/reynolds.html (Reynolds Number)=(Inertial Forces)/(Viscous Forces) My question is: Force of drag Fd=? Wild guess: Fd=Inertial Forces?

I was wondering; Imagine two situations: 1) I rotate an axle with a strong magnet attached within a conductive coil (a dynamo). 2) I rotate an axle with a strong magnet attached without a conductive coil. Does the presence of a coil (and therefore the generation of current in the coil)...

Homework Statement A ball of mass 0.5 kg traveling horizontally through the air with speed v(t) experiences a drag force DT (t) whose magnitude is given by: DT (t ) = 0.01[v (t )] 2 The speed of the ball is found to reduce from 10 m/s to 8 m/s over a time interval t, during which time...

Homework Statement I'm trying to crudely approximately the distance individual masonry units fly when a blast load impacts a masonry wall. I'm a structures guy so I can calculate when the wall will failure, but I am having trouble with the calculus associated with the equation of motion. My...

A golf ball without dimples experiences more drag because the deflection area of the airflow around the ball is larger which means that the pressure drop behind the golf ball is also higher. The increased drop in pressure creates a suction vacuum behind the golf ball which pulls it back and...

1. Homework Statement The small scale drawing given in the Annexure shows the general arrangement and dimensional data on an early version of the English Electric “Canberra” B.1 bomber, powered by two Rolls Royce “Avon” jet engines. It was and is an extremely successful aircraft, designed by W...

Homework Statement The small scale drawing given in the Annexure shows the general arrangement and dimensional data on an early version of the English Electric “Canberra” B.1 bomber, powered by two Rolls Royce “Avon” jet engines. It was and is an extremely successful aircraft, designed by W E...

Drag On A Sphere... Confused...? I've been looking at the Adidas Jabulani football from the recent soccer world cup and came across this issue. This ball has many grooves and ridges on it's surface, and also has less seams (as it is constructed from fewer panels), and these seams are shallower...

Hello all, I recently made some model rockets and thought it would be fun to predict their height before setting them off this weekend. I thought it would also be interesting to compare the difference in the predictions of a model with no drag and a model with quadratic drag. Surprisingly...

Okay, thanks Hikaru and K2 for your help on the accelerated drag problem. Now I have another drag related problem I wonder if you you help me with. Say a car is put in a wind tunnel and is measured to have the following attributes: Frontal Area: Ax Side Area (Right): Ay Frontal Coefficient of...

I've been doing some research on sphere aerodynamics, in particular that of soccer balls, and was wondering if there was any way to separately calculate the pressure / form drag, and also the surface / viscous / skin drag. I know that Stoke's Law of F=6(pi)RnVc, where R is the radius of the...

We have \dfrac{d}{dt}\left(\dfrac{\partial \mathcal L}{\partial \dot{q}_j}\right)-\dfrac{\partial \mathcal L}{\partial q_j}=-\dfrac{\partial \mathcal F}{\partial \dot{q}_j}. If the force of friction is F=-kv^2 how do you go about calculating \mathcal F My idea is as follows F=-kv^2...