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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199 views

Find the force needed to accelerate body to a certain velocity for a certain time with respect to drag force

So, the problem is straightworward when we suggest that air resistance force is constant: $$ \vec F = \frac {\vec V_1 - \vec V_0} {t} m / b $$ $$ \vec V_0, \vec V_1 - \text {initial and final ...
5
votes
3answers
388 views

Terminal velocity after vertical launch

If an object is launched directly up at its terminal velocity, will it have enough time/energy to reach its terminal velocity again before it hits the ground, or will drag prevent this? In this case, ...
-4
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1answer
68 views

Why fall bombs always in a horizontal position? [on hold]

I´m not sure but it seems to me when bombs are dropped they always fall in a horizontal position. Which is to say, not with their nose down. What´s the reason for this?
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1answer
20 views

External and internal resistance to airflow

If an aircraft was travelling at 100mph an hole was opened to allow 100mph into the cabin,then the airflow is feed into an amplifier like a ramjet and the airflow out of the ramjet was increased to ...
5
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4answers
2k views

Does gravity slow down a horizontally thrown baseball?

I have a simple question: Does gravity slow down a horizontally thrown baseball? Assuming when a baseball is thrown it has a vertical velocity as well, does it slow does the ball? Any help is much ...
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1answer
22 views

Spin on the rack

Bike mounted on hitch rack. Why wheels spin constantly while I drive? I can't find anything on the internet. The kids in the other cars love to watch them
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0answers
26 views

What is the relative velocity term in drag and lift force in the following case?

When a stationary particle is introduced in a fluid moving with horizontal velocity $V_fx$, what is the relative velocity terms in the drag force ($F_D$) and lift force ($F_L$) equations. Am I correct ...
13
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4answers
17k views

After what speed air friction starts to heat up an object?

I understand that air friction cools off an object at low speeds. For example, if you blow on a spoon of hot soup, it cools off. Or if you swing a hot frying pan in the air, it cools off faster. But ...
1
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1answer
108 views

Air friction at supersonic velocities

I know that if an object moves in the air, it can experience two types of drag, laminar and turbulent. For instance, I have a meteor of ideal spherical shape falling from edge of space, say, 100 km up ...
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2answers
32 views

Velocity over time applying constant power and considering air drag

I wanted to understand how velocity changes over time when applying a constant power to a body of mass $m$. I figured out that in this case, since $$P=d/dt(KE)=d/dt(\frac{1}{2}mv^2),$$ integrating I ...
2
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3answers
8k 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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0answers
19 views

Magnitude of Drag force correction on a bean bag

I am currently designing a ballistic launcher for an engineering project. Our task is to propel a bean bag approximately one hundred grams in mass ten feet with the lowest standard deviation possible. ...
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3answers
473 views

Projectile, air resistance and wind

So for my school project I am working on a projectile simulator and air resistance. So I have looked at this. Equations for an object moving linearly but with air resistance taken into account? ...
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0answers
49 views

How high does an arrow fly, when shot straight up in the air?

How high will an arrow fly, when shot straight up in the air ? There is already a similar question, but it neglects the air resistance I would like to know how significant is the air resistance. Is ...
4
votes
3answers
336 views

How does mass affect the distance a ski jumper travels

I did an experiment to explore this. My results found that their is an optimum mass of a ski jumper. I am unsure about the maths behind this. Can anyone help.
30
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3answers
6k views

If we threw a baseball from the ISS, could we deorbit the ball?

Clearly this is a hypothetical question. Say we bring a star baseball player into NASA, prep them appropriately for a mission in space, and fly them up to the International Space Station. They go on ...
0
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0answers
677 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
175 views

Application of Stoke's Law

I was looking at Stoke's law and it says that you use it to calculate the drag force on a sphere passing through a fluid. Can i also use this equation to calculate the drag force on a car going ...
3
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1answer
319 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
50 views

Can drag force and lift force be in the same direction in the following case?

In the attached picture, can I say that there is a lift force in the Y-direction, and a drag force too in the same Y-direction? $F_L$ proportional to $V_fx^2$ ? $F_D$ proportional to $V_py^2$ ? Is ...
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3answers
44 views

Is drag force in the direction of particle motion or opposite to motion?

Suppose water is flowing in horizontal direction (positive $x$-direction) and a particle immersed in that water is also moving in the same direction. In this case, is the drag force $F_D$ in the ...
1
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1answer
42 views

Conditions for free fall

What are the conditions at which free fall occurs? If a body is falling freely under the effect of gravity only without external resistance, the motion is called free fall. This definition gives me ...
1
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1answer
38 views

100 lbs of drag? Really? Chain running physics

Recently came across this video of an endurance technique involving the strapping of a 100lb chain to one's back and running along the grass dragging it behind. What is the true force experienced by ...
3
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1answer
5k 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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1answer
14 views

Do dimples reduce laminar drag across a surface?

My question is about laminar flow across a smooth surface. I have read about how the eddy currents, caused by dimples, at the surface help a blunt object travel through the air with less drag as in a ...
5
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2answers
779 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. ...
2
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2answers
438 views

Why does spinning a golf ball one way make it go further than spinning it the other way?

In golf, you'll often hear people say that one person hits the ball further than another because the one person "draws" the ball while the other "fades" it. I want to know why the direction of ...
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1answer
34 views

what causes airborne bodies to tilt?

Imagine a Helium-inflated oblate spheroid floating still (A). Buoyancy force cancels gravity force on Y axis. Object is tied to ground with a rope. If a wind force is applied on X axis, why does the ...
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0answers
16 views

power of an engine with wind

I know the power of an engine to overcome air drag is $1/2 c_d ρAv^3$. If the speed of the car $25\ \mathrm{m s}^{-1}$ (relative to the ground) and it travels in opposite direction to a wind at a ...
4
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1answer
64 views

Explaining the shape of a raindrop and a drop of mercury

I saw on wikipedia that the shape of a raindrop is explained by using Laplace pressure. But why? Since the drop is in motion, we shouldn't be able to use an hydrostatic law, am I wrong? ...
4
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2answers
173 views

Fired a bullet upwards, can it fall down and kill me?

I know that if something is thrown up with a velocity v, it comes down with the same velocity as long as its motion faces no resistance. So is it possible for me to fire a bullet and be killed if it ...
1
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2answers
78 views

Solving Projectile Motion Equation with Drag [closed]

Previously, I was helped in solving a projectile motion equation to model the velocity of the projectile with respect to distance with drag taken into account by using differential equations (which I ...
2
votes
2answers
1k views

What would be an appropiate shape for a parachute?

I'm trying to design a parachute that minimizes the descent velocity, but I'm not sure what shape I should use. From what I've read, ellipse-shaped parachutes are too aerodynamic and minimize drag, ...
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3answers
63 views

If two objects have the same drag coefficient, but one is much heavier, would it fall faster?

Not sure this is a good example but imagine we have two feathers, both with exactly the same drag coefficient, they have the exact same shape and everything, but the only difference is that one of ...
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2answers
23 views

Model velocity as function of distance in object subject to drag and propulsion

Given an initial speed $v_0$ and acceleration $\frac{dv}{dt}|_0=a_0$, I need to find velocity as a function of distance knowing that Drag is $ D = Av² $ Propulsion is $P = Bv + C$ I already found ...
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3answers
37 views

Modelling an Airplane Question

For an assignment of mine I am creating a very basic model of an airplane, where I choose to consider a fixed amount of parameters that affect flight and to disregard others which I find too difficult ...
0
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1answer
50 views

Ball touching the side of a tube — DOUBT

I have a small doubt in understanding a physics concept. If a steel ball is dropped in a thin tube of glycerol, it will eventually reach its maximum or terminal velocity. However, if the steel ball ...
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1answer
68 views

Calculate constant acceleration needed to reach terminal velocity at specific time [closed]

I'm trying to find a way to calculate a constant acceleration given the following: One dimensional motion. The only forces involved are the force ($F_a$) caused by a constant acceleration ($a_c$) ...
0
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1answer
440 views

How can the Air friction force be applied to an object?

Suppose we have an object and we throw it straight upward in the air. How do we apply the Air friction force to this object while moving upwards and after that downwards? Sorry if it's easy because ...
0
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1answer
114 views

Projectile time of ascent not equal to the time of descent?

Why is the time of ascent less than the time of descent in a projectile motion. I understand that while going up the air resistance and gravity act downwards and while coming down gravity is ...
0
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1answer
52 views

Terminal Velocity in Water

Another question concerning classical physics. On Earth, the combination of air resistance and gravity interact in a way that creates the phenomenon of terminal velocity. Do other fluids (for example, ...
2
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3answers
169 views

Rate at which a pendulum bob slows due to air resistance?

I know that "perfect" pendulums would be able to swing forever, unperturbed by air resistance. However, since there is air resistance around us, pendulums (swinging bobs) slow down and move closer and ...
27
votes
5answers
13k 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 ...
0
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1answer
47 views

Motion in space

Does a space shuttle travelling in space experience any resistance to its motion? If a body in space is applied constant force, does it attain speed of light after sufficient time?
2
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2answers
1k 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 ...
2
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4answers
3k views

Does a ski racer with a larger mass have an advantage?

Does a ski racer with a greater mass have an advantage over a racer with a lesser mass? If mass of one racer is 54 kg and the mass of a more slender racer is 44 kg I know the speed at which they ...
1
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0answers
21 views

Feasiblity of a long spinning top using an electromagnet to pull on Earth's magnetic field

Would it be feasible to build a infinitely spinning top (ref. Inception) by including a battery powered electromagnet who's polarity flipped in sync with the top's rotation such that the pull against ...
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1answer
57 views

Is air friction active force or constraint force?

Can air be regarded as a constraint body when a rigid body is moving? Or is the moving itself cause the friction so it is an active force?
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3answers
146 views

Free Fall with Air Resistance

Can somebody help me understanding why when free falling the force on the vertical axis is F= -mg-kv, where k is the constant of air resistance and v the velocity? Suppose the vertical axis is ...
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1answer
84 views

Quadratic drag projectile motion

I have calculated formulas with 1 dimensional trajectory motion (free-fall) including quadratic drag, and have created the following equations. These equations of motion are not of much use on its ...