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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1answer
532 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. ...
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240 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 ...
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43 views

Force of air lift

Say I want to find out how much wind force I would need to lift a tank 10 meters in the air, given I already know its dimensions. Is there a formula for that?
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406 views

Opposite of air resistance - Calculating the force

For a project on school I am making a program that can visualize physics in a two dimension space. Not the relativistic and quantum physics, but just the standard high school stuff. One of the things ...
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67 views

Air resistance from several angles

Could one by using only 3 coefficients of air resistance, one for each axis $x$, $y$ and $z$, model the resistance on an object from any angle? So for example if one has a square, could one summarise ...
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Air resistance causing decrease in time of flight of a projectile

If the air resistance causes a vertical retardation of 10 percent of value of acceleration due to gravity, then the time of flight of a projectile will be decreased by nearly? Take $g= 10 \frac{m}{...
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1answer
125 views

Damped Harmonic Oscillator Scenario

Suppose we have the following setup, a mass on a spring attached to a wall, as shown in the diagram: We are completely ignoring friction between the mass and the ground here, and we have an ideal ...
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1answer
83 views

What's the drag coefficient? [closed]

Suppose an objects starts with velocity $v$. A damping force that is dependent of velocity acts on this object ($F=-\beta v$). After traversing distance $l$, the object has velocity $\alpha v$ with $0&...
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230 views

Stokes' law for disks [duplicate]

Stokes' law of viscous friction is famously applicable to spheres in (slow) motion within a fluid. If the object has radius $r$ and speed $v$, and the fluid has dynamic viscosity $\eta$, the dampening ...
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Why large excavated holes can create air currents?

My friend shared this post on my wall, but I got doubt: How can a hole like this create air currents which suck helicopterss also? I didn't really understand.
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1answer
73 views

Acceleration-Velocity function to Velocity-time function with non-constant acceleration

I've faced this question when trying to solve a test problem I had. The test, of course, did not require those functions to be expressed, but I just had to know what's going on. We're given a body ...
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1answer
40 views

How to account for velocity term in force component of equations of motion?

I am trying to solve for a coefficient of drag that creates a certain situation. The situation is at a high speed, so the drag at high velocity equation applies: $$ F_D = \frac{1}{2}\rho v^2 C_d ...
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3answers
715 views

Distance travelled by an object slowed only by drag?

Let's say I throw an object horizontally off a cliff with a fixed height, and I know the time it takes to fall. I wanted to know how far it travels, but it has an acceleration opposite the direction ...
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1answer
1k views

What slows down a fidget spinner more: air resistance, or friction from the bearing?

So "fidget spinners" are now massively popular. I got one, and it occurred to me that I'm not sure which force is more important in slowing them: friction in the bearing, or air resistance acting on ...
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2answers
639 views

If two objects have same density but different size,which one will drop first?

The greater the mass, the higher the terminal velocity. But what if the object's size (area) also increase, will the air resistance cause the heavier object to become slower than the lighter object?
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Did Newton know or assume that planetary (extraterrestrial) space was frictionless vacuum-space?

For a correct calculus of the perpetual orbital motion of planets as determined by Newton’s laws of gravitation, frictionless motion through interplanetary vacuum space would have been a prerequisite. ...
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272 views

How to correctly determine the stopping distance of a coasting bicycle when considering aerodynamic drag?

Given values of $C_{rr}$, $C_{d}{A}$ and $\rho$(Air density) how can I correctly determine the distance and time taken to coast from some $\upsilon$1 to $\upsilon$2?
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Theory behind the relationship between the mass of a cylinder and the time taken for it to roll down an incline - air resistance?

I conducted a simple experiment where I tried to find the relationship between a cylinder's mass and its time taken (or average speed or acceleration, which can be easily derived from the time & ...
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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 ...
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95 views

Do all masses with equal mass density, whatver their form is, reach the same end velocity, falling from infinity to the surface of earth?

Is the end velocity for every object (regardless its form) the same when it reaches the face of the earth (the object's mass is negligible with respect to earth) from infinity? Let's assume the ...
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1answer
161 views

Standard linear solid model - dashpot “short out” at $t=0$

My professor said that at $t=0$ the dashpot in standard linear solid is "short out". Why? I know that the force of dashpot is ($u$ is the dislplacement): $$F_{\eta}=\eta \space \frac{du}{dt}.$$
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2answers
611 views

Turbulent flow and Separated flow

My knowledge in aerodynamics is very limited as I am doing just an introduction to the subject, and so I may not understand very complex explanations. I know that at some point laminar flow becomes ...
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2answers
2k views

Terminal Velocity of a Car

When explaining how a car reaches its terminal velocity, is it solely down to how aerodynamic the car is? My thoughts are that if you have a fixed mass $m$, then the contact frictional force will be ...
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1answer
391 views

Proving Drag is a Non-Conservative Force

I wanted to show that a force such as drag is not a conservative force but cannot apply my method of approach. Suppose we took the situation with drag at high speeds, so $\vec D=c|\vec v|\vec v$ for ...
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71 views

Why do ball makes curvature? [duplicate]

Case 1: when a player kicks the ball in soccer game Case 2: When a fast bowler swing the ball in cricket In both cases the ball makes a curvature. How this happens ? Is there any Law of Physics ...
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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 ($C_d$). ...
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How does a helicoper auto-rotate? The force of the air pushing on all blades would equal out. Wouldn't it?

So, I was learning about helicopter and how they auto rotate and I learned that when the engine fails the helicopter starts to fall and the air is thrown up at the blades which turns them like a ...
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1answer
517 views

Upthrust (Floating and sinking of objects)

When an object is wholly submerged and displaces its own volume of fluid and the weight of the fluid balances with the weight of the object, the object floats. But following Newton's first law, if the ...
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396 views

Mechanical energy when ball is falling

I could not understand why mechanical energy of ball is not constant when time passes when a ball is falling in liquid with terminal velocity.
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1k views

Why doesn't car fuel/energy consumption scale like the cube of the velocity?

The power required to overcome drag is relative to speed cubed. When I'm driving $100 km/h$ my car consumes $~10 $litres/$100km$. At $200 km/h$ the consumption should be $2^3 × 10$ litres/$100km = 80 $...
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79 views

Let me rephrase I am helping my daughter learn physics. is it possible to determine mass from data that has only distance the object fell and time [closed]

The assignment is already over. I helped her figure out how to determine acceleration, and a rough estimate of air drag, but I was wondering if it is possible to determine mass. I have searched many ...
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1answer
310 views

Do liquids have terminal velocities?

Consider a liquid free-falling through a fluid (i.e. dropping the contents of a bucket full of water from a high building). Will it reach a terminal velocity? I know that the terminal velocity of an ...
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1answer
200 views

Why does a tail make a kite more stable?

I have looking online to find answer to this question and one answer said that the tail increases drag and weight but, it did not say why the Increase in drag makes the kite stable. One theory I have ...
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Why is friction proportional to normal force? [duplicate]

Surely, if you have 2 surfaces interlocking then a horizontal force would also result affect the force of friction. It seems unintuitive that friction is only proportional to normal force. Is there ...
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1answer
346 views

How a quadcopter works

I was reading this slide about how a quadcopter works. Since my physics is at a very basic level, I don't understand 3 things: 1.The drag seems to be always higher than the thrust for the same RPM. ...
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1answer
36 views

Air resistance in experiment about measuring Gravitational acceleration

In my experiment, I use MBL sensor and drop volleyball and tennis ball and I measure gravity acceleration. But mechanical energy wasn't preserved because of air resistance. I found two expressions: $$...
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1answer
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period of a pendulum immersed in water

Does the value of $g$ change inside a dense fluid? How would the time period of simple pendulum change when immersed in water?
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4answers
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Terminal velocity on the moon? Is it possible and how long would it take? [closed]

Is there a way to find this out? If so please tell me the formula or just tell me how much time would it take for a 100 lb human to reach terminal velocity
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6answers
991 views

Distance from a velocity time graph where acceleration is not constant [closed]

In the following question I calculated the distance with methords actually only applying to constant acceleration. I thought this applicable because the question was asking for an approximation. I ...
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1answer
330 views

Air resistance for practical purposes?

Doing a physics experiment where we are required to calculate the acceleration from gravity, for a simple high school assignment. And as part of an extended discussion, I would like to take into ...
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1answer
71 views

How can i calculate the speed of a fan in a commercial jet engine?

How can i calculate the speed of a fan in a commercial jet engine if i already know the ρ(Air density), Cp (Maximum output), A (Rotor swept area), V(wind speed) and Drag coefficient? and what other ...
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2answers
542 views

Trajectory with air resistance angle to hit target

How do I calculate the angle required to hit a target, I found this at Wikipedia: http://en.wikipedia.org/wiki/Trajectory_of_a_projectile This works very well but my problem is, that in my case air ...
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4answers
1k views

Distance to reach terminal velocity in a viscous liquid

I have a physics exercise tomorrow and it's about a ball falling through a viscous (olive oil, ricin oil) liquid in a tube. I know this is not needed there but I would like to ask how to compute the ...
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Why do flat objects land softly?

I noticed that if you drop a flat surface, parallelly from a relatively low height, onto another, the impact is almost cushioned. What is happening here? Is this to do with the air, especially near ...
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1answer
663 views

Free fall and terminal velocity

An object in free fall is defined as one that is moving solely under the influence of gravity. So if an object has reached terminal velocity(force of gravity is cancelled out by upwards force of ...
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1answer
86 views

Is it more efficient to load or tow a vehicle?

If I had a truck (a U-haul or similar) and needed to move a four-wheeled car from one location to another, would it require less energy (fuel) to load the car into the truck or tow it behind? A ...
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1answer
64 views

Heat shields and the atmosphere

Space capsules and the Shuttles were equipped with heat shields to protect the spacecraft and those on board from the tremendous heat generated from friction as they reentered earth's atmosphere at ...
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1answer
351 views

Most aerodynamic shape

What are the theoretical condition for a shape to be more aerodynamic? How can you design an aerodynamic shape without any experiment,just with equations?
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146 views

Why do rifles impart rotation to bullets?

I have read at this site and at google that rotation of the bullet corrects the deviation from the target. Does anyone know how this is achieved?
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55 views

Ohm's law for stones

Suppose I drop stones from a height. Now, we define quantity analogous to electric current called mass current. Now, to get an analogue to Ohm's law, we need drift velocity for stones. For electrons, ...