What is Air resistance: Definition and 415 Discussions

In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, drag force depends on velocity.Drag force is proportional to the velocity for a laminar flow and the squared velocity for a turbulent flow. Even though the ultimate cause of a drag is viscous friction, the turbulent drag is independent of viscosity.Drag forces always decrease fluid velocity relative to the solid object in the fluid's path.

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  1. S

    Calculating effects of air resistance on a falling mass

    Calculating effects of air resistance on a ball of mass 0.67kg, being dropped from a height of 4.93m. I have worked out theoretically what time it would take without air resistance using s=ut + 0.5at(squared) however i cannot find an equation that will factor in air resistance. thanks
  2. Nim

    Free-fall formula, adding air resistance

    How do you add air resistance to these 2 equations? #1 sqrt(2 * d / g) = time until impact #2 sqrt(2 * d * g) = velocity on impact The equation for air resistance is: Fd = 0.5 * Air Density * Velocity ^2 * Frontal Area * Drag Coefficient How would you combine this equation with the above...
  3. G

    Combating Air Resistance on a Bike

    I'm trying to calculate the torque i would need to pedal when in the highest gear on my bike to sustain a constant speed on level ground. Basically i just want someone to review my calculations and make sure they're correct. I leg press 270 pounds and therefore each of my legs can supply 135...
  4. G

    Calculating force of Air Resistance

    I'm having a little trouble calculating the force of air resistance for a bicycle. The formula I used is: Fd=1/2pv^2ACd . p= 1.3kg/m^3 v= 13.44 meters/sec. A= 1.15 meters^2 Cd= 0.9 I got an answer, but I don't know if it is correct, can someone please verify?I got 121.52 Newtons.
  5. M

    Air resistance in relation to ballistics

    Having this discussion on another board, basically stemmed from one member saying that a bullet would be in flight for "over 5 seconds"in response to something else someone said about a 0.50 caliber sniper rifle firing at a target 2 miles away. I figured that negating air resistance, the time...
  6. M

    Calculating Air Resistance Force: Table Tennis Ball Falling at 8.2 m/s

    Homework Statement A table tennis ball of mass 10 g is falling towards the ground with a constant speed of 8.2 m/s. Calculate the magnitude and direction of the air resistance force acting on the ball. Homework Equations Not quite sure The Attempt at a Solution m= 10 g which...
  7. M

    Projectile Motion: Solving Equations with Air Resistance

    Hi Im trying to make an equation for a projectiles path, but this is only over a very short distance, so the projectiles curve aren't taken into account. I am including the air resistance. This is what i have done: m*dv/dt=-k*v2 Differential: dv/v2=-k*dt integrated: -1/v=-k*t+C when: t=0 og...
  8. S

    Effect of Air Resistance on the Speed of a Thrown Ball

    I understand that in the absence of air resistance, if a ball is thrown vertically upward with a certain initial speed, on returning to its original level it will have the same speed. But when air resistance is a factor, will the ball be moving faster, the same or more slowly than its...
  9. M

    Work done by air resistance and gravity

    Homework Statement A baseball is hit high into the upper bleachers of left field. After the ball lands in the bleachers, what is the work done by gravity and the work done by air resistance? Wouldn't they both be zero because they are acting 90 degrees to the path of displacement?
  10. B

    Air glider question and air resistance

    Homework Statement Early test flights for the space shuttle used as a glider (mass of 980kg). After a horizontal launch at 480 km/h at a height of 3500m, the glider eventually landed at a speed of 210 km/h. What would its landing speed have been in the absence of air resistance? also, what was...
  11. L

    Air Resistance of coffee filter

    Homework Statement You drop a single coffee filter of mass 1.4 grams from a very tall building, and it takes 47 seconds to reach the ground. In a small fraction of that time the coffee filter reached terminal speed. a) What was the upward force of the air resistance while the coffee filter...
  12. G

    What is the maths behind projectiles (including air resistance)?

    E.g. A football of mass 1kg is thrown with a speed of 10m/s at an angle of 30 degrees from a horizontal plane. Take air resistance (in Newtons) as 1/15 th of the speed of the ball in the exact opposite direction that the ball is traveling. How long is the ball in the air? and how far...
  13. P

    Air Resistance and drag coefficien

    Homework Statement An object of mass 10kg is projected upwards (from ground level) with initial velocity 60m/s. It hits the ground 8.4 seconds later. Find the drag coefficient, k. Homework Equations dv/dt + rv = -g, where r = k/m The Attempt at a Solution I have used the...
  14. L

    Air Resistance of bicyclist problem

    A bicyclist rides 6.2 km due east, while the resistive force from the air has a magnitude of 2.7 N and points due west. The rider then turns around and rides 5.5 km due west. The resistive force from the air on the return trip has a magnitude of 2.2 N and point due east. Find the work done by...
  15. H

    Air resistance on a rotating cylinder

    Hi, I have an object that's rotating in the air with constant speed. Now a bit simplified it could be looked as an uniform cylinder that's rotating round and round (not like a propeller). How would air resistance affect this rotation and how could you describe this force with a formula? Thanks
  16. P

    How Does Air Resistance Affect Projectile Motion?

    Homework Statement A particle is projected vertically upward with a speed v0 under the influence of a drag force that is proportional to the particle's speed. As the particle falls back down, its terminal speed is vt. (a) Find the time it takes to reach ymax (b) Find ymax (c)Show that...
  17. C

    Air resistance with Projectile Motion.

    I have a quick question... when you launch a projectile with no air resistance, the optimal launching angle is 45 degress with no air resistance, but when you add air resistance into the equation, the optimal launching angle for distance changes. Does air resistance make this angle bigger or...
  18. D

    Air resistance of a thrown object

    an object thrown vertically upwards into the air takes shorter time to reach its peak height than it does to return to the height of the throw, is this true, how can it be, on the way up it has both the airs resistance ang gravity working against it whereas on the way down only the resistance...
  19. R

    Speed of light and air resistance

    Does the speed of light slow down due to air resistance? I often hear about how the speed of light is constant in a vacuum, and I'm assuming it has something to due with it being different in air due to air resistance. If so, why is this? Since light has no mass, shouldn't air not have an affect...
  20. T

    Help on inclined plane and air resistance.

    Homework Statement Hey, As an end of the year easy grade, our physics teacher assigned us a 20 point project in where we design a lab and analyze the data in a power point. I chose to use an inclined plane and a roller cart. My idea was to analyze the effect of a sail (thus creating air...
  21. A

    Projectile Motion with Air Resistance problem

    hi. Suppose that a projectile of mass "m" is launched, from ground level in a horizontal plain, making an angle teta to the horizontal .(with air resistance).now in which angle "m" has the maximum range? .(our teacher said that we should find 53 degrees for teta).please prove it. (first of all...
  22. G

    Vertical trajectory with air resistance

    Homework Statement a particle P of mass m is projected vertically upwards with velocity U_0\mathbf{k} in a uniform gravitational field -g\mathbf{k} with air resistance proportional to the square of the velocity. This is a five part question for which I have found the solutions but there is one...
  23. B

    Average force of air resistance

    [SOLVED] Average force of air resistance In early test flights for the space shuttle using a "glider" (mass of 1500kg including pilot), it was noted that after a horizontal launch at 750km/h at a height of 4500m, the glider eventually landed at a speed of 300km/h. What would it's landing speed...
  24. V

    Air resistance in pendulum experiment

    hey guys, I've been experimenting with a pendulum and while doing the error discussion for my experiments i got stuck with the air resistance involved... I've used the formula to find the force applied by the air resistance to the pendulum and ended up with F=2,76*10^-5 *v^2 . (v= velocity of...
  25. O

    How Does Air Resistance Affect a Bullet's Terminal Velocity?

    [SOLVED] Air resistance Homework Statement A bullet of mass m, diameter d, and muzzle velocity v0 is fired vertically upward from the ground. Assume that the drag can be expressed with Prandtl's air resistance forumla and that the drag coefficient, c, and air density, p, are constant. Find...
  26. G

    2 Masses on a spring and a rocket with changing mass and air resistance

    Homework Statement Two mass m1 and m2, connected by a massless spring of force constant k, are at rest in equilibrium on a smooth horizontal table. A velocity of magnitude v and direction away from m2 is imparted to m1. a.) Find the speed of the center of mass. b.) Determine the speed of m2...
  27. H

    Is Free Fall Possible Without Air Resistance?

    Hey guys, when an object is free falling, is it still under the effects of air resistance? If it was not under the effects (an environment without air resistance) is free fall possible? (I am looking for an argument that it is under the effects of free fall but all replies will be taken into...
  28. J

    Projectile with a linear air resistance force question

    Homework Statement OK I hope someone will help me with this For a projectile with a linear air resistance force Fs =−mkv, show that the maximum horizontal range is given by the equation (v0 + g/k)(x/u0) + (g/k^2)ln(1 - kx/u0) = 0 where u0 = V costheta, v0 = V sintheta are the...
  29. B

    Solving ODE Problem: Air Resistance Proportional to Velocity Squared

    [SOLVED] ODE problem Homework Statement A situation in which the air resistance is proportional to the velocity of an object squared. Object dropped off of a building with height 100m. F = -mg + Fr Fr=.5*cw*p*A*v^2 cw=.5 p = air density = 1? Homework Equations I need to...
  30. S

    Finding Range of Projectile Under Air Resistance

    I have made a program in Matlab to plot the path of a projectile with air resistance, however, I am lost as to how to obtain an equation for the range. I have found my displacements in the x and y direction by solving second order differential equations, it would be far too difficult to set the...
  31. S

    What is the impact of air resistance on projectile motion?

    Hey, I have a question about how to calculate the air resistance, and eventually how much more energy is required to get the same result, once air resistance has been factored in. I have thought of two ways to solve the problem: One way requires multi-variable calculus, which I havn't had...
  32. J

    Tossing upward with air resistance

    Could someone tell me if my approch to this is correct? I am given the change in vertical v final(zero), v initial, mass, and frictional coefficient. The question askes for distance. I set up the equation vf^2=vi^2+2ad(mg(frictional coefficent))
  33. R

    Projectile motion with air resistance and ball of mass

    Homework Statement A ball of mass "m" is thrown vertically upward with a velocity of "vi." It experiences a force of air resistance given by F=-kv, where "k" is a positive constant. The positive direction for all vector quantities is upward. Does it take longer for the ball to rise to its...
  34. G

    How Does Air Resistance Affect the Speed of a Falling Pine Cone?

    A 0.25 kg pine cone falls from a branch 20 m above the ground. A) With what speed would it hit the ground if air resistance could be ignored? m= 0.25 kg g= 9.8 m/s^2 d= 20 m Ep= (0.25kg)(9.8m/s^2)(20m) = 49 J Ek= 1/2mv^2 49J = 1/2(0.25kg)(v^2) 2(49 J = (0.5kg)(0.5 v^2)) 98 J =...
  35. G

    Work Done by Air Resistance on rain drops

    Homework Statement A 2.76 x 10^-5 kg raindrop falls vertically at constant speed under the influence of gravity and air resistance. After the drop has fallen 131m, what is the work done by gravity? After J is found for gravity, what is the work done by air resistance in units of J. Homework...
  36. B

    What is the average air resistance for a person?

    I can't seem to come up with a decent formula/accepted value for air resistance. I realize there are things that need to be taken into account, but I am already delving into things way beyond what I've done per the course work, and I don't want to bite off more than I can chew. I understand...
  37. C

    Air Resistance free fall problem

    Homework Statement What is the threshold or percent accuracy (100% like plus-minus 10%) of a freefall with air resistance? Homework Equations % accuracy = (actual_free_fall_time)/(ideal_free_fall_time) Computed Free Fall Time based on 9.8m/s^2 net force towards the ground. Actual...
  38. N

    Drag force (air resistance) and acceleration

    Homework Statement A baseball is thrown straight up. The drag force is proportional to v^{2}. In terms of g, what is the ball's acceleration when its speed is half its terminal speed and a) it is moving up? b) it is moving back down? Homework Equations \sum F=ma mg + bv^{2}=ma - When...
  39. P

    Velocity with air resistance help

    I need to find the velocity with the following information. V=Vo+AT and A=G-KV so how would i find what V equals from this: V=Vo+(G-KV)T
  40. X

    Difficult air resistance problem

    1. In a shotput event, a 2kg shotput is launched from a height of 1.5m with an initial velocity of 8m/s at an angle 60degrees to the horizontal. The formula R=0.0000378.v^2 gives the force due to air resistance (R) where v is the instantaneous velocity. Find the ratio of the gravitational force...
  41. O

    Webpage title: Air Resistance of Baseball: Quadratic vs Linear Drag Force

    When a baseball flies through the air, the ratio f_{quad} / f _{lin} of the quadratic to the linear drag force is given by \frac{f_{quad}}{f_{lin}} = \frac{cv^{2}}{bv} = \frac{\gamma D}{\beta} v = (1.6 x 10^{3} \frac{s}{m^{2}}) Dv. Given that a baseball has a diamater of 7 cm, find the...
  42. E

    Rock Off Cliff: Greatest Speed?

    Homework Statement 1. A person throws three identical rocks off a cliff of height h with exactly the same speed v0 each time. Rock A is thrown vertically upward, rock B is thrown straight out horizontally, and rock C is thrown straight downward. If we ignore the effects of air resistance...
  43. N

    What is the acceleration of a falling rock with air resistance?

    I'm trying to figure out this problem... A rock of mass 49 kg accidentally breaks loose from the edge of a cliff and falls straight down. The magnitude of the air resistance that opposes its downward motion is 249 N. What is the magnitude of the acceleration of the rock? I know that I...
  44. H

    Force of air resistance in wind tunnel

    Homework Statement I am working on making a small wind tunnel using a 20" fan. What i want to figure out is the force generated by the movement of air. I want to make the size of the tunnel shrink to help induce more velocity in the air (see picture). Homework Equations Bernoulli's...
  45. P

    How do i calculate air resistance?

    hi i can't work out how to find air resistance:confused: i am designing/making a paintball sniper rifle. I have worked out the potential fps and need to work out air resistance. Thanks:rolleyes:
  46. G

    Air resistance on a falling person

    If we model the air resistance on a falling person as being proportional to the square of that person's speed, in certain circumstances the proportionality constant between the air resistance and the square of the speed is equal to 0.100 kg/m. Part A What would be the terminal velocity of a...
  47. B

    How Much Force is Needed to Climb a Hill at Constant Speed with Air Resistance?

    Homework Statement If a bicyclist of mass 68.0 kg (including the bicycle) can coast down a 6.90 degree hill at a steady speed of 5.80 km/hr because of air resistance, how much force must be applied to climb the hill at the same speed (and the same air resistance)? Homework Equations The...
  48. M

    Calculating Air Resistance for a 5kg Rock Falling at 7m/s2

    A 5kg rock falls with an acceleration of 7m/s2. What is the magnitude of the force of air resistance acting on the rock at this instant?
  49. T

    What affects the swing of a pendulum w/ and w/o air resistance

    Homework Statement I'm having troubles figuring out what affects the swing of a pendulum. Hypotheses: 1) The period is dependent on the amplitude 2) The period is dependent on the mass of the bob 3) Air resistance and friction will affect the period 4) The period is dependent on the...
  50. T

    Air resistance and Air density?

    I've never worked with air resistance before so any help just getting me started would be much appreciated. Homework Statement A 20 kg object falls free from a height of 15 m. Including air resistance, what will its position be after 0.6 seconds? Air density is 1.11 kg/m^3. Homework...
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