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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Torque of Air Resistance on Ellipsoid

Imagine an non-rotating arbitrary free, rigid ellipsoid with in some arbitrary direction with velocity $\vec v$. Assume linear drag ($\vec F=KA\vec v$ for some constant K, where A is the cross section ...
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2answers
2k views

How long until we fall into the Sun?

As a planet moves through the solar system, a bow shock is formed as the solar wind is decelerated by the magnetic field of the planet. Presumably the creation of this shock wave would cause drag on ...
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218 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 ...
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2answers
1k views

What would a person experience in a free-falling elevator in a shaft long enough to reach terminal velocity?

Assume we had an elevator shaft long enough for a free-falling elevator to reach terminal velocity. As I understand it, when the elevator begins to fall a person inside would experiences ...
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0answers
175 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 ...
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2answers
7k views

Finding the drag force (Air resistance force) for accelerated ball?

As you know if I want to find the force for an accelerated object I will use the law $F_o=ma$ so I can get the affecting force of it. But there is another force affecting against the object. It's the ...
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4answers
1k views

How do I calculate the distance a ship will take to stop?

I am a River Pilot and drive ships for a living. These ships are very large and range up to 160,000 Metric Tons. I am trying to figure out how to calculate the distance to stopping. I have a basic ...
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0answers
665 views

Problem understanding free fall with water resistance

Please take a look at the picture below before read my question: As you see in the picture the object A is floating on the water because the $F_{drag}\gt F_{grav}$ obverse the object B is sinking ...
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1answer
118 views

Calculating Mass for a Reduced Trajectory while Keeping Projectile Force Constant

Apologies if this is not a research-specific question, but applied mechanics. A firefighter has to pass a test in which he is to throw a medicine ball a certain distance. The ball is thrown at a 45 ...
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1answer
134 views

How much energy is consumed by a aircraft to maintain a speed of sound? [closed]

Let's assume that the aircraft is 1000kg and it is flying in a air density of 1.225kg/m^3 at the speed of sound in air. Just how much energy does it require per second to maintain flying at this ...
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1answer
170 views

Do celestial objects experience drag from the near vacuum of space?

For instance do the planets around the sun experience drag from the near vacuum of space? Or do the (hydrogen) atoms in interplanetary have a mean velocity near orbital speeds? And if so would (small) ...
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1answer
662 views

Is there another way to calculate the work done by air resistance?

A ball of mass $0.37\text{ kg}$ is thrown upward along the vertical with a initial speed of $14\text{ m/s}$, and reaches a maximum height of $8.4\text{ m}$. a) What is the work done by air ...
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1answer
465 views

Does the Magnitude of the Drag Coefficient on a Rectangular Prism vary with Rotation?

I have a question about the drag coefficient in the drag equation. Let's say I have a rectangular prism oriented such that, looking down on it, the long side is parallel to the y-axis. Moving forward ...
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1answer
101 views

Are the forces I'm using correct? (ball in air) [closed]

I have been working on a program which should simulate all the forces on a spherical object. Right now those are balls, but they can easily be changed to something else. These are the formulas I use ...
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1answer
596 views

Drag force at high speeds [duplicate]

The drag force on a spherical body according to Stokes' law is given by $$F = 6π\mu rv$$ Where $\mu$ is the dynamic viscosity of the fluid, $r$ is the radius of the spherical object, and $v$ is its ...
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2answers
142 views

What processes occur when a meteor enters the atmosphere?

What processes occur when a meteor enters earth's atmosphere and then what will be speed of meteor when it encounters air resistance?
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1answer
361 views

How would you swim in inviscid water?

The viscosity of water creates drag on swimmer's body so its effect is to slow down the swimmer. However the viscosity seems to be essential for pushing the water backwards by the swimmer's arms and ...
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2answers
256 views

Aerodynamics drag of hollow cylinder vs solid cylinder of the same cross area?

I wonder how a hollow cylinder at the same cross area perform vs a solid one, i.e the hollow cylinder has larger radius? I guess they have a similar drag, is that true?
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3answers
344 views

Does fire create air resistance?

Does fire create air resistance/drag? So, for example, would it be harder to swing a flaming sword than a normal one?
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2answers
485 views

How to calculate air resistance of penny dropped from Empire State Building?

If a penny is dropped from the Empire State Building, then its speed, without taking air resistance into consideration, is $\sqrt{\left(32\frac{\textrm{ft}}{\textrm{s}^2}\right)(1454\textrm{ ...
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4answers
9k views

Terminal velocity of all falling objects is same?

Ideally 2 objects of different mass and weight will hit the floor at same time because they face same gravitational pull and accelerate. Will the terminal velocity of both objects be same also? and ...
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1answer
2k views

In tennis, why does topspin serve bounce higher than flat serve?

When receiving servers (while playing tennis), I've noticed that the tennis ball seems to bounce up higher on me when the server uses a topspin serve than when the server hits a flat serve. Why is ...
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2answers
204 views

How to calculate time for ball to reach plane while considering mass, gravity and wind resistance?

The scenario that I'm having is such that a ball of radius $15mm$ is thrown from a location point $\vec{p}=(2, 5, 2)$ in a direction of $\vec{d}=(3, 0, 4)$. The initial velocity is $30m/s$. There were ...
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2answers
994 views

Could some design of a propeller be used in both air and water?

Propellers in water are smaller in diameter. They also move more slowly. On the other hand, aircraft propellers are larger in diameter, have narrower blades and operate at very high speeds. An ...
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3answers
469 views

Parachute in vacuum

Consider that the earth is vacuum. Consider a person of weight 100 kg is falling from sky with an parachute . He is free falling at height of 3000 m. When will he reach the ground? What would happen ...
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0answers
283 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, ...
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2answers
1k views

Concerning drag on a flow past a cylinder

I am wondering about the drag coefficient for a flow past a cylinder. I am reading this article. I understand why the drag is high to begin with (point 2), when the boundary layer separates and the ...
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4answers
4k views

What causes a soccer ball to follow a curved path?

Soccer players kick the ball in a linear kick, though you find it to turn sideways, not even in one direction. Just mid air it changes that curve's direction. Any physical explanation? Maybe this ...
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2answers
5k views

Explanation that air drag is proportional to speed or square speed?

A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ...
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3answers
2k views

Projectile Motion with Drag

The overall goal is to write a Mathematica program that will compute the launch angle that will yield the greatest range with using [RandomInt] function, but I was having trouble with the physics. In ...
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1answer
2k views

Drag on a spinning ball in fluid

I am a physics newbie (high school level) and I am wondering what happens when a spherical object is spinning on the spot in a bunch of gas (no gravity here, just an imaginary physics sandbox). Am I ...
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2answers
688 views

Why is simple harmonic motion called so?

Is the motion of a simple pendulum, a simple harmonic motion? It stops vibrating after sometime.
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1answer
468 views

Skiing downhill

The other day on skiing holiday we've been arguing about whether an adult has weight advantage over a child when skiing downhill. I was claiming that gravity is a constant regardless of object's ...
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3answers
249 views

If an electric car were to drive without having to stop, would the range be greatly affected by the speed at which the vehicle is moving?

Of course aerodynamics factors into this question, and the faster you are moving the more air you have to push out of your way, the more energy you use. But would the difference be only a small ...
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2answers
347 views

Forces on an aircraft - thrust, lift, drag, weight

I'm extremely sceptical about the wikipedia page on aircraft flight mechanics. When describing 'straight climbing flight', it says: lift is unable to alter the aircraft's potential energy or ...
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1answer
491 views

Does the metal foam “whiffleball” orbital reentry idea make any sense?

Planetary Resources is a company speaking publicly about mining near Earth asteroids for resources. I'm interested the physicality of a claim they make in a video here: ...
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0answers
236 views

How much force is required to hold an umbrella?

Assuming a small umbrella (e.g. http://www.amazon.com/ShedRain-WindPro-Umbrella-Close-Size/dp/B001DL5WN0). What are the factors that need to be considered? I assume where I hold the umbrella might ...
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1answer
373 views

How would you use the Euler-Lagrange equation to predict the motion of projectiles with linear (Stokes) drag (but no wind)?

My first instinct would be to use the force $$\vec{F} =- \alpha \vec{v}$$ and therefore $$V(\vec{r}) = \alpha \int_C \vec{v}\cdot d\vec{s} = \alpha \int_C \vec{v}\cdot \vec{v} dt = \alpha \int_C ...
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2answers
1k views

Finding optimal angle for projectile, taking into account linear (Stokes) drag

If you throw a projectile from the ground at a certain angle, it's not hard to see that, assuming we're in a vacuum, throwing it at 45º from the ground will always make it go farthest before it hits ...
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2answers
221 views

Estimating atmospheric friction by measuring the change in velocity of a ball thrown straight upwards

Imagine I throw a ball straight upwards with some velocity $v_1$, and filming the ball with a camera, I can estimate a velocity $v_2$ (along the same vector) after the ball has moved a distance $D$. ...
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2answers
3k views

Work done by the air resistance [closed]

A ball of mass 0.37 kg is thrown upward along the vertical with a initial speed of 14 m / s, and reaches a maximum height of 8.4 m. a) What is the work done by air resistance on the ball? b) ...
7
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1answer
897 views

Equation for the trajectory of a frisbee?

I'm the lead programmer on a FIRST robotics team, and this year's competition is about throwing Frisbees. I was wondering if there was some sort of "grand unified equation" for Frisbee trajectory that ...
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2answers
166 views

Estimating drag due to wind - ribbon-shaped sail

In the countless calculations and discussions concerning the "space rope" I've never found any addressing its capability to resist winds. Consider, as in most current works, it's a 1m wide ribbon, ...
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1answer
496 views

Is resistance to motion directly proportional to the speed of a moving object?

Power is known to be equal to the force x velocity (P=FV). Im solving a question that states the following : Car with engine working at 32 kW, mass of 1 tonne, travels at a constant speed of 40m/s ...
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1answer
380 views

Limitations of drag equation

The magnitude of the air resistance for objects with Reynolds numbers greater than 1000 is given by the formula: Why it does not hold for objects with lower Reynolds numbers? Can I use this ...
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2answers
639 views

Minimum size of an asteroid to actually impact earth

From what I understand, an object entering the atmosphere will start to burn up from the tremendous resistance of the atmosphere. Presumably, for asteroids under a certain size, they will burn up ...
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0answers
101 views

Integration question from book “e: The Story of a Number” by Eli Maor [closed]

In the book 'e: The Story of a Number', a derivation of a parachutist problem is given on pg. 109-110. A parachutist jumps from a plane and at $t=0$ opens his chute. At what speed will he reach the ...
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2answers
185 views

Is air drag equation in term of momentum still valid?

This is the known equation of air drag: $$m{\bf a}=mg-\mathcal D=mg-b{\bf v}.$$ Considering this, is air drag equation in term of momentum still valid? $$m{\bf v}=mv_g-b{\bf r}.$$
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4answers
5k views

Acceleration of two falling objects with identical form and air drag but different masses

I have a theoretical question that has been bugging me and my peers for weeks now - and we have yet to settle on a concrete answer. Imagine two balloons, one is filled with air, one with concrete. ...
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1answer
1k views

Projectile Motion with Air Resistance and Wind

I am wondering how the general kinematics equations would change in the following situation. If an object were fired out of a cannon, or some sort of launcher, so that it had both an initial velocity ...