# Tagged Questions

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.

1answer
284 views

### How to calculate the actual drag force on a wing?

I want to calculate the actual drag force that a NACA 63-412 wing would experience at a given planform area and relative wind speed. Airfoiltools gives a drag coefficient of 0.01676 for the optimal ...
2answers
146 views

### Working out velocity (including air resistance) [duplicate]

For my computing project, I am creating a projectile simulator but I cant seem to get my head round the air resistance. I tried by working out the horizontal and vertical velocity by solving it (...
2answers
177 views

### Calculate damping constant / coefficient

I am trying to graphically simulate a series of springs in 2D. Now one of the forces I am stuck with calculating is the damping force. The given formula is $F = -k_d v$. I know that $v$ is the ...
0answers
82 views

### How velocity progresses over time with a non-constant acceleration? [closed]

A $0.25\text{ kg}$ sphere of radius equal to $0.07\text{ meters}$ is dropped from rest from the top of a building. Granted that it will not hit the ground before, when and after what distance ...
1answer
300 views

### What forces act on an object submerged in flowing fluid in an enclosed environment (i.e pipe)?

Let's say we have a pipe with water flowing through it and obstacle is inserted into the pipe and is rigidly fixed to the inner wall so that it does not get washed away. What forces are exerted by ...
2answers
282 views

### Air Drag in orbit

Artificial satellites don't orbit the earth forever. Eventually the Earth's atmosphere, thin as it may be up there, will bring them down. But did you know the linear speed of a satellite in a near ...
3answers
171 views

### Air resistance force [closed]

How do I find the air resistance force and the maximum air resistance force when all I'm given is the mass, terminal velocity, and I know it's falling in quite air? I found a formula online but it ...
1answer
76 views

### Why does a parachute open up faster on Mars than on Earth? [closed]

I recently heard that a parachute opens up much faster on Mars than on Earth. Why is that the case? More specifically, during a NASA Edge TV program, one of the scientists working on parachute tests ...
4answers
681 views

### What is the friction force at terminal velocity?

As terminal velocity is inversely proportional to viscosity or fluid friction, then my question is: at terminal velocity, the fluid friction is maximum or zero?
1answer
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### What is the force required to move a raindrop?

I'm doing some research on how much force is required to move a typical raindrop (assuming that it is falling straight down) off to the side of X distance. This is for a school project on creating our ...
2answers
263 views

### Where does the loss of kinetic energy of the wind flowing over an airfoil go?

When an airfoil is tested in a wind tunnel the speed of the wind behind the airfoil is less than speed of the wind in front of it. That means the wind loses kinetic energy. The reason for that is drag ...
1answer
126 views

### How can we theoretically calculate the number of balloons needed to stop a bullet?

After watching this video, I am interested in proving it mathematically. The problem is that how can we apply the conservation of momentum here to find the velocity of the bullet while we don't know ...
1answer
164 views

### How size of objects lifted by the wind depends on the speed of the wind?

What are the sizes of the objects that could be picked up and flown by tornados, depending on the tornado's speed? To put it another way, assuming turbulent flow and object density much higher than ...
2answers
242 views

### A big cannon to match a ballistic missile? [closed]

During the last years of WW2 the Germans used ballistic missiles V-2 (with payload mass ~1,000 kg) to bombard London, from a distance about 300 km away. Suppose the British could respond by building a ...
2answers
1k views

### If an object falls - regarding air resistance - does the Potential or Kinetic energy get converted into thermal energy as it is falling?

I read a paragraph on the transfer of potential energy to kinetic energy and heat from this website: Even if air resistance slows down the ball, the potential energy is the same (Mb x g x H). ...
1answer
100 views

### How do I do non constant acceleration questions?

Okay, so there is a type of question that keeps coming up in past papers and I can't seem to crack it. The one I'm doing now is: A skier initially travelling at $50~\text{m/s}$ along a ...
3answers
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### Reason for motion after terminal velocity

Let some object hang by a string. So no motion since weight was counter balanced no net force. Now string is cut. Object is falling under gravity and experiences air resistance. Terminal velocity is ...
1answer
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### Space and motion

When we throw a ball upwards sitting in a running bus or train it directly comes to our hands but when we do the same sitting on a moving motorcycle the ball falls backwards. Why?
1answer
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### Why doesn't a parachutist, according to Newton, “fall” upwards (because drag is larger than gravity)?

Part of the second law states that an object will accelerate in the direction of the unbalanced force. However, I've been thinking about parachuting and skydiving a bit lately, and I know that when ...
2answers
66 views

### What are the major differences in group-skydiving as opposed to “single” skydiving?

Surface area/the cross-sectional area is greatly increased, so my thinking is it should decrease terminal velocity as well as a couple of other factors. But mass changes too (since there would be more ...
1answer
1k views

### Calculate a drag force on a sphere?

Objective Work out a drag force for a unit sphere traveling through air at velocity. Values for formulae are below. The context of this question is that I am calculating this in an atmospheric ...
2answers
2k views

### Which ball falls faster, the cool one or the hot one?

Suppose we're on the top of the Tower of Pisa (or a larger version of it) with two identical cannonballs. We heat one up (say, to 200 degrees Celsius, or some other high temperature before it starts ...
0answers
67 views

### Wind resistance on moving body

Suppose that a vehicle is traveling 60 km/h north, and the wind speed is also 60 km/h going the same direction, would there be wind resistance, and to what extent? Also, if I put my hand outside the ...
2answers
117 views

### Reasons for decaying orbit for satellites and spacecrafts

As per newton's law, unless a force is applies, moving objects will continue to move in a straight line. A satellite which speeds at around 17.5k mph would be travelling in a straight line considering ...
1answer
223 views

### Drag versus centripetal force

I'm trying to see how extensive a gaming engine's physics are. Consider a spinning disc with a box on it which is free to spin around a vertical pole connecting it to the disc. The pole is more ...
2answers
103 views

### How to actually account for air resistance?

What's interested me in my studies thus far is that in a lot of beginner undergrad mathematics and physics courses we're often told to calculate trajectories, velocities, etc. by "ignoring air ...
2answers
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### Will terminal velocity exist on this imaginary planet?

If the atmosphere of an imaginary planet is really thin like 100 particles per cubic centimeter (density of the closest resemblance of vacuum made on Earth) and has mass say, 15 times than that of ...
2answers
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### Will a bullet dropped and a bullet fired from a gun horizontally REALLY hit the ground at the same time when air drag is taken into account?

In a world without air, I understand they definitely would. However, with drag taken into account, I think they wouldn't. Since the drag force varies proportional to the square of speed (ignoring the ...
1answer
347 views

### Simple air resistance experiment

I have a paper plate, and I'm taping paper streamers to it. I have 0, 1, 2, 3, and 4 streamers. I tried to place the streamers at places equidistant from the next. 2mm are attached to the plate and ...
1answer
81 views

### Newton's law of resistance [closed]

Anyone can give me some clues on how this can be proved? What kind of drag force is used? A particle is projected vertically upward with an initial speed $v_0$ near the Earth's surface. Show that ...
6answers
6k views

### Force required to drive car

From what I know of Newtonian Mechanics, if an object is moving at a constant velocity, the net force acting on that object is equal to zero. If there is friction, then the applied force required to ...
2answers
316 views

### Does drag produce heat?

When a solid object moves through a fluid drag is produced. Does this drag produce heat? I believe drag should produce heat as it is the friction between fluid and surface of object. Is this true or ...
1answer
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### Work due to air resistance

I was trying to find the distance a machine system I designed would potentially go. The machine works like this: A mass $M$ drops down and through a system of pulleys, pulls a wheel wound with the ...
1answer
159 views

### Friction because of Earth's rotation

Is there some force of friction that acts on bodies due to rotation of Earth?. We all know earth is an non inertial frame. If there is some frictional force is there some way to prove it?. What I mean ...
2answers
391 views

### Is there a difference between “No Air Resistance” and "Constant Air Resistance''?

Is there a difference between "No Air Resistance" and "Constant Air Resistance''? Like for example if we have two identical objects with different masses and we drop them from the same height. Will ...
2answers
118 views

### Does a ball spin more from left to right than it does from right to left?

I swear that in a manual on tennis published by the German Tennis Association (Deutscher Tennis Bund) it stated as fact that all things being equal a ball will move more from left to right than from ...
1answer
256 views

### Explain the terminal velocity equation [closed]

As explained by Method 1 on WikiHow, the equation for Terminal Velocity is: $$V_T = \sqrt{2 \times m \times g \over ρ \times A \times C}$$ Some parts of this equation are self explanatory, and ...
2answers
798 views

### Do wind turbines convert the kinetic energy of air?

It is often said that wind turbines convert the kinetic energy of the wind into electricity. But in respect to horizontal wind turbines with airfoil shaped blades this is imho not the case. Wind ...
1answer
772 views

### How can I estimate the density of fog?

I'm working on investigating the effect fog has on drag. I have assumed an air density of $1.225 \frac{\text{kg}}{\text{m}^3}$ for dry air, but I don't know what value for density I could assume that ...
1answer
68 views

### Which moves faster in a time $t$: $A$ or $B$? [closed]

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 $B$ ...
1answer
554 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 ...
3answers
7k views

### Benefits of rear spoiler in cars

What would be the benefits of rear spoilers in cars, like this one:
3answers
333 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 ...
1answer
75 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 ...
2answers
54 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 ...
1answer
105 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 ...
1answer
170 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 non-...
3answers
3k 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 ...
2answers
475 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 ...
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 (...