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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Projectile motion, solved with perturbation theory [on hold]

A ball is dropped from rest, the initial height is $h_1$. There is air resistance given by $-mkv$. In the downward motion, the equation of motion can by written as $$\dot v = -g-kv$$ with the y ...
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1answer
56 views

Which moves faster in a time $t$: $A$ or $B$? [on hold]

Suppose we have two objects, $A$ and $B$, both made of the same substance. They also have the same shape (e.g. two spheres), but $A$ is larger and therefore more massive than $B$. Both $A$ and $B$ ...
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0answers
20 views

Falling with air resistance speed as a function of distance [closed]

Starting at 0 velocity and falling with air resistance $-mkv$, find the relation between speed and the vertical distance that an object falls. I went through the problem to find the equation of motion ...
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1answer
37 views

Projectile motion with air resistance limit question [closed]

I have the equation for the max height $h$ of a projectile launched directly upwards with speed $v_0$ and air resistance force $-mkv$. I am trying to calculate the limit as $h$ goes to ...
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1answer
50 views

Equation for Terminal Velocity on an inclined plane and the time it takes to reach it

Now I'm doing a research on the matter similar to this thread : Terminal Velocity of identical shape/size objects which is very self explanatory and very helpful. However in my case, the objects will ...
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3answers
497 views

Benefits of rear spoiler in cars

What would be the benefits of rear spoilers in cars, like this one:
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3answers
145 views

Two bodies of equal mass thrown from a height-Practical physics question

I have a doubt about this question: Two bodies of masses $M$ and $m$ are allowed to fall from the same height. If the air resistance be the same for each of the bodies, will the two bodies reach ...
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1answer
24 views

How to find the maximum height with a loss of 5 J of energy due to air drag [closed]

Can someone please help me to figure out how to use the 5J of energy into my equation for the maximum height. I know that the maximum height is given by, $$h_{max}={(v_f-v_i)^2 \over 2g}$$ but I'm ...
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2answers
41 views

Who feel more impact of fall

A person jumping from a higher building is likely to suffer less injury than the person jumping from a short building as the person from large building fall long enough to attain drag force which ...
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1answer
49 views

Projectile motion with drag force of the form $\vec f =-k \vec v$ [closed]

An object is fired with initial velocity $v_0$ at inclination angle $\theta$ above the horizontal. Drag force in the air is taken into account and is of the form $\vec f =-k \vec v$. Knowing that the ...
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1answer
119 views

What is the physical interpretation of the linear coefficient in this ODE for projectile motion?

For the second order ODE governing the position of a projectile subject to air resistance $$ m\frac{d^2x}{dt^2} +k\frac{dx}{dt}+mg=0 \quad k>0, \> x(0)=0, \> x'(0)=V>0 $$ a ...
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1answer
62 views

Drag force on a flat plate

The solution for this apparently is $\frac{1}{2}C \rho A V^{2}$ where $C$ is the drag coefficient, $A$ is the area and $\rho$ and $V$ are the wind density and velocity. Let's do it without the drag ...
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2answers
95 views

Why do we use less fuel by driving at constant speed?

It is common practice to drive at constant speed as much as possible to reduce fuel consumption, or at least to avoid "pumping" on the throttle (at frequencies high enough that the lowpass filter does ...
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4answers
4k views

Why doesn't a tied balloon behave like a pendulum?

It is well known that a tied weight will oscilate under the effect of gravity if left from aside, like a pendulum. However, if we tie a helium balloon to the ground from and left it form the floor ...
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2answers
42 views

The effect of windspeed on a car

I've worked problems in the past in trig class concerning the effect of wind on the speed of a plane and it's flight path and was wondering if a similar thing occurs with a car. First off, I'm ...
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0answers
27 views

How to calculate the ship resistance caused by water viscosity

If there is a ship going in the sea at 50km/h, and a length of 5m, width of 2m, how do I calculate the ship resistance caused by water viscosity? in other words I want to calculate the drag Force that ...
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1answer
140 views

Calculating time to reach certain velocity with drag force

I was given a problem for homework where we needed to calculate the time for a falling object to reach a certain velocity when accounting for drag force. I did it by setting up acceleration as a ...
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0answers
42 views

Drag - Dimensional Analysis / Buckingham Pi

Dimensional Analysis / Buckingham Pi Theorem I'm working on dimensional analysis and I'm having trouble. Here's a problem from my book I'm working on for practice. I'm suppose to consider a small ...
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1answer
44 views

Buoyancy / Drag Problem

Buoyancy / Drag Problem Just a little bit of help would be nice. I have a spherical particle of radius $R$ and density $\rho$, surrounded in a fluid of density $\phi$ and viscosity $\eta$. I'm ...
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0answers
63 views

Projectile under quadratic air resistance force

So here's the problem background: A projectile of mass m is shot straight up with initial velocity $v_0$ and feels a quadratic air resistance force of the form $F = −kv^2$, where $k ≡ mg/u^2$. ($k$ ...
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1answer
43 views

Is air resistance affected by both mass and surface area?

If so, which has the biggest impact?
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1answer
43 views

Projectile with air resistance [duplicate]

If you have a projectile with these variables. $x_0 = 1v_{0x} = 70, y_0 = 0, v_{0y} = 80, a_x = 0, a_y = -9.8$ I know how to plot these points with this equation. $$ x = x0 + (v_{0x})t + 1/2((a_x)t^2) ...
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1answer
140 views

Add air resistance to projectile motion

I am given an initial x and y position and initial velocity and I was asked to graph the trajectory in 1 second intervals. This is what I have so far: If $x_0 = 1, v_{0x} = 70, y_0 = 0, v_{0y} = 80, ...
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3answers
238 views

What factors determine whether wind resistance will have an important effect?

What factors determine whether or not wind resistance will have an important effect on the trajectory of a projectile?
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1answer
30 views

What is the work done below proportional to? [closed]

A raindrop falls from a certain height to the ground, with a terminal velocity u. The viscous force is F = 6*3.14*n*r*v, where n is the coefficient of viscosity, r is the radius of the raindrop, and v ...
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0answers
46 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}=\; ...
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2answers
271 views

What is the terminal velocity of a sheep?

Inspired by this question on Gaming.SE Using actual in-real-life physics, what would the terminal velocity of a sheep actually be? I would assume it would be around 50m/s, but I might be wrong. ...
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2answers
106 views

Confused about the theoretical origin of quadratic air drag [duplicate]

Though the mathematical concepts underlying quadratic air drag are quite straightforward (a single variable differential, just like the linear drag equation), my text book (and online text books) ...
2
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1answer
70 views

How to calculate the drag coefficient using terminal velocity?

I was wondering if it were possible to calculate the drag coefficient by allowing an object to reach terminal velocity. Can you rearrange the terminal velocity formula to give the drag coefficient?
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2answers
1k views

How much more efficient is a road bike than a mountain bike? [closed]

What would be a good estimate on the difference of efficiency between a road bike and a mountain bike? A number of links cite all the usual reasons: thinner tires, better aerodynamics... But I'm ...
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2answers
92 views

Time of flight for a projectile with stated initial velocity and size at various distances

I've been mooching round the internet looking for an answer to this one and can't find a ready resource, hence the question. In short, I'm trying to discover the flight time of a shotgun pellet at ...
29
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5answers
4k views

Which ball touches the ground first?

This is a very well known problem, but I can't find an answer in the specific case I'm looking for. Let's consider two balls : Ball 1 weighs 10 kg Ball 2 weighs 1 kg Balls have identical volumes ...
0
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0answers
26 views

Drag on a conductor moving in a uniform magnetic field

Given a conductor moving through a perfectly uniform magnetic field, what is the drag force experienced by the conductor (due to induced eddy currents, or any other magnetic interactions I may have ...
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2answers
723 views

Why do co-rotating vortices coalesce, but not counter-rotating ones?

In studying the aerodynamics of modern aircraft equipped with high-lift devices, I have discovered that quite a number of distinct trailing vortices are present in the immediate wake of an airplane in ...
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4answers
105 views

Is it possible to prove that projectiles with drag will not travel in a parabola under the theory of classical mechanics?

Can you prove that projectiles will travel in a parabola, provided the acceleration due to gravity $g$ does not vary significantly along the trajectory? This should take air resistance into account. I ...
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2answers
196 views

How should I throttle my rocket to reach highest altitude? [closed]

"Real world" problem. Suppose we want to launch a rocket equipped with an engine which can be throttled as we prefer. Suppose also that the amount of fuel burnt per time is directly proportional ...
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3answers
1k views

Does an object's kinetic energy increase, decrease, or stay constant when it reaches terminal velocity while falling?

Does an object's kinetic energy increase, decrease, or stay constant when it reaches terminal velocity while falling?
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4answers
327 views

Experiment - Measuring final velocity of a parachute

I'm working on a project that involves a scale parachute. It is vital for the project to get a good measurement of the speed it has when it lands. We still haven't built the parachute, but we need a ...
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1answer
81 views

Follow up question regarding: Deceleration rate of objects of different mass but the same otherwise

My first question was answered here: Deceleration rate of objects of different mass but the same otherwise . But based on that, here is a follow-up question (I also edited my first post with the ...
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2answers
96 views

Deceleration rate of objects of different mass but the same otherwise

Using a tennis ball as an example object, if one ball weighs 1 ounce and the other is 2 ounces, and both are struck at 100 mph on the same trajectory, would there be any difference in the deceleration ...
2
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1answer
74 views

Uses of the Reynolds number

I have seen a lot of places talking about the Reynolds number and how it is calculated, but I have never seen an equation that actually made use of this number to calculate lift, drag, or other ...
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6answers
4k views

Why do heavier objects fall faster in air?

We all know that in an idealised world all objects accelerate at the same rate when dropped regardless of their mass. We also know that in reality (or more accurately, in air) a lead feather falls ...
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1answer
61 views

Projectile trajectory with linear air resistance [closed]

I have the following equations $$\ x′′(t)=−\frac km x′(t)$$ $$\ y′′(t)=−\frac km y′(t) - g$$ where $k$ is the drag, $m$ is the mass of the object and $t$ is the time. $g$ is the gravity constant. ...
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2answers
85 views

Calculating the rate at which a car turns

This is going to be difficult to describe, as I have no real concept of this sort of physics, so please bear with me. If this is too much or beyond the scope of this website, I apologize. I am making ...
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3answers
182 views

Would an airplane flying through superfluid helium experience lift and drag?

Would an airplane flying through superfluid helium experience lift and drag? The airplane is presumed cold enough to not heat up the helium.
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1answer
135 views

Upthrust vs Drag

24: A ball is falling at terminal speed in still air. The forces acting on it are upthrust, viscous drag and weight. What is the order of increasing magnitude of these 3 forces? ...
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1answer
183 views

Small Animal Terminal Velocity

I recently saw a cat fall probably 100 feet like in this video Cat Falls. It seemed as if the cat reached terminal velocity by the time it hit. Does this mean that cats (and other small animals) could ...
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1answer
244 views

Why aren't airplanes like golf balls?

Ok this is a silly question but here it goes Although it is good to have a laminar flow of the air around the object for low drag but the laminar flow is prone the phenomena called separation (sounds ...
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60 views

Relationship between the fall time and projected area

I am investigating the relationship between the fall time of a paper tray and its projected area. In this investigation I have been using the following variables: Controlled Variable: The air ...
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2answers
162 views

If the MH370 black box did sink to 15000 ft, how long would it have taken?

I have been following MH370 on the news just as everyone and latest reports seem to indicate that the black-box could be found. A recent info-graphic http://t.co/lyBBE9C2hF shows the insurmountable ...