What is Terminal velocity: Definition and 224 Discussions

Terminal velocity is the maximum velocity (speed) attainable by an object as it falls through a fluid (air is the most common example). It occurs when the sum of the drag force (Fd) and the buoyancy is equal to the downward force of gravity (FG) acting on the object. Since the net force on the object is zero, the object has zero acceleration.In fluid dynamics, an object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the fluid through which it is moving.As the speed of an object increases, so does the drag force acting on it, which also depends on the substance it is passing through (for example air or water). At some speed, the drag or force of resistance will equal the gravitational pull on the object (buoyancy is considered below). At this point the object stops accelerating and continues falling at a constant speed called the terminal velocity (also called settling velocity). An object moving downward faster than the terminal velocity (for example because it was thrown downwards, it fell from a thinner part of the atmosphere, or it changed shape) will slow down until it reaches the terminal velocity. Drag depends on the projected area, here, the object's cross-section or silhouette in a horizontal plane. An object with a large projected area relative to its mass, such as a parachute, has a lower terminal velocity than one with a small projected area relative to its mass, such as a dart. In general, for the same shape and material, the terminal velocity of an object increases with size. This is because the downward force (weight) is proportional to the cube of the linear dimension, but the air resistance is approximately proportional to the cross-section area which increases only as the square of the linear dimension. For very small objects such as dust and mist, the terminal velocity is easily overcome by convection currents which prevent them from reaching the ground and hence they stay suspended in the air for indefinite periods. Air pollution and fog are examples of convection currents.

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  1. I

    Drag time of terminal velocity?

    Hi all! How can we know the time and speed of the object before it reachs the terminal veocity, it will reach that, but when? (he's acceleration decreseases right) thanx
  2. D

    Terminal Velocity of Cube: 1.6 m/s

    Homework Statement cube has a drag coefficient of 0.90. What would the terminal velocity of this cube be, 1.0 cm on a side in air (ρ = 1.2 kg/m3)? Take the density of this cube to be 1.6 x 103 kg/m3. A 68 m/s B 1.6 m/s C 5.6 m/s D 20 m/s E 360 m/s Correct answer...
  3. B

    Hyperbolic tangent function for terminal velocity with Vo>Vt

    Hi! First post on this forum, though not the first time visiting :) I am working on a model of an object falling from one layer of air density into another layer with a higher density, effectively changing the acceleration from positive to negative instantly. (Somehow I am thinking of positive...
  4. M

    Reason for motion after terminal velocity

    Hi, 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 reached when weight is equal to the air resistance. So no net force and no net acceleration...
  5. B

    Terminal Velocity: Student Investigation & Incorrect Book Answer

    This is not a homework question. It is basic physics. The question in the book relates to terminal velocity. I think the answer in the book is incorrect. Please advise. Students are investigating how the area of a parachute affects the forces acting on it in freefall. Steel balls are attached...
  6. P

    Does a Falling Object Ever Truly Reach Terminal Velocity?

    Today in physics we talked about terminal velocity. This got me thinking. As air resistance acts on a falling object, the acceleration of that object will decrease. I was wondering if terminal velocity is only approached asymptotically and never technically reached. Please explain this. Thanks.
  7. S

    Terminal Velocity of a skydiver

    Homework Statement [/B] A skydiver, initially undergoing a high acceleration, is approaching her terminal velocity. At a given instant, the fluid friction (due to air resistance) on the diver and her diving gear is 680. N [up] and the unbalanced force causing the acceleration is 40. N [down]...
  8. J

    Terminal Velocity: How does one explain why the squirrel gets undamaged?

    Let me begin with a fragment quoted from the textbook I'm using: 1. Homework Statement A squirrel (with ##0.0155\ m^2## of its body facing the fluid) falls from a ##5.0\!-\!m## tree to the ground. Estimate its terminal velocity. (Use a drag coefficient for a horizontal skydiver.) What will...
  9. P

    Kinematic Problem: MJ & SP Meet - Find Distance

    Homework Statement MJ falls from rest from a tall building. 1.5 seconds later SP throws himself downward with an initial velocity of -45 meters per second. Find the distance where they meet. variables: α1= -9.81 α2=-9.81 Δγ1 = ? Δγ2=? Δ†1=? Δ†2=? + 1.5 ∨i1=0...
  10. HamzaPhysical

    How long does it take to free fall from Mt. Everest?

    1.If i were to jump of of Mt. Everest (29,090 ft), how long will it take me to hit the ground? The initial velocity is 0, the pull of gravity is equal to 9.81m/s^2(acceleration). I got 42 seconds, but i didnt calculate terminal velocity so I am pretty sure my answer is wrong to calculate time...
  11. kubaanglin

    Terminal velocity in a vacuum?

    If an object is dropped in a hypothetical infinitely long vacuum tube, will it reach a terminal velocity? I assume that it must because according to Einstein, no object that has mass can travel at the speed of light. My guess would be that the terminal velocity of an object in a vacuum would...
  12. A

    IB Physics Extended Essay - Terminal velocity experiment - ideas neede

    Hi. I decided a month or so ago, that I am going to do my physics extended essay on the topic of terminal velocity. However, at the moment I am not sure what experiment I can do. At the beginning I thought I would do an experiment where I would drop bodies made of cardboard with different...
  13. S

    Does a terminal velocity exist?

    Does a terminal velocity exist? Like when a free falling body is under the influence of gravity, does it stop accelerating after a certain velocity? If yes.. What's that velocity?
  14. B

    Why Do Objects Only Reach 95% of Their Terminal Velocity?

    Hi forum! Why can't falling objects reach terminal velocity in the real world? When an object drops (W = mg) it will experience drag force upwards. And since drag is proportional to velocity, both force will eventually be equal therefore, the object will not accelerate anymore, hence reaching...
  15. B

    How Long Does It Take a Person to Reach Terminal Velocity?

    I want to estimate how long it will take a person (I could specify their dimensions and density :P but maybe just take it as 170 cm tall, 80 kg, etc.) to fall a certain height in the gravitational field of the Earth, not neglecting air resistance. I'm looking at heights anywhere from say 30 m...
  16. G

    Mechanics question derivations terminal velocity (quadratic case)

    hi so basically my question is derivation of derivation of the quadratic case of the terminal velocity I have attached the pictures in picture 1 I don't know I think the book has error in his derivation @ equation 2.4.13 shouldn't it be + instead of negative ?? & in second picture their...
  17. A

    Distance to reach terminal velocity

    Homework Statement A body with a 100 Kg of mass is falling , what's the distance and time to reach terminal velocity? Homework Equations a=dv/dt v=ds/dt drag force= 100v^2 F=ma The Attempt at a Solution I don't really need the numbers , just the expressions I don't know how to...
  18. A

    Distance to reach terminal velocity

    I know how to get the terminal velocity , how to get the time , I need to know how to the distance , I know it has got something to do with turning v to ds/dt , but I can't figure it out
  19. M

    Finding cross-sectional area from terminal velocity.

    Homework Statement The aerodynamic drag on an object moving through air is proportional to Av^2, where A=cross-section, and v=velocity. The terminal velocity of a person without a parachute falling through the air is about 56m/s. Estimate the area of the cross-section of a person seen from the...
  20. A

    Air Resistance (Drag Force) and Terminal Velocity

    Homework Statement "How does air resistance affect terminal velocity" Homework Equations N/A The Attempt at a Solution I know most of the answer of this, however I am just wondering say take a parachutist for example, if the air resistance is the resultant force, then in order...
  21. M

    Relativity and terminal velocity

    Hi If I had an object and a very long evacuated tube. Presumably the object with only the force of gravity acting on it would continuously accelerate and hence would have no terminal velocity. However we know that it cannot go faster than light. If my long tube is say pointing towards the...
  22. J

    Terminal Velocity of Ice Pellet: Homework Solutions

    Homework Statement An ice pellet drops from a cloud 1.5 km above the Earth's surface. It's spherical so its drag coefficient is 0.45 and it has radius 0.1 mm. The density of air is 1.2 kg/m^3 and the density of ice is 910 kg/m^3. What is the terminal speed of the ice pellet? When the pellet...
  23. A

    Variable acceleration and terminal velocity

    Homework Statement A cube is falling from a height of 200 m (initial velocity =0) , it reaches it's terminal velocity . Given that :its mass is 100 kg , cross sectional area 40 cm2 and coefficient of drag 2. Putting only weight and drag in consideration , calculate its terminal velocity and...
  24. E

    Distance Needed to Reach Terminal Velocity

    Homework Statement I am completing a homework assignment that involves a python program for air resistance. One of the questions in the assignment asks us to find the minimum distance needed to reach terminal velocity. The air resistance is quadratic. The mass of the object is .5kg and its...
  25. B

    Question on Terminal Velocity finding time

    Homework Statement I have two skydivers umping out of a plane at 5000m . Skydiver A is using extended arms and reaching a terminal velocity of 41.53m/s. Skydiver B jumping 20 second later headdown and reaching a terminal velocity at 90 m/s. The question is to find the time the second diver...
  26. M

    Cycling on the Moon, no air resistance to cause terminal velocity.

    Homework Statement Imagine a cyclist (in spacesuit) cycling on the level on the Moon (so no drag). The external forces acting on them are contact force upwards (from Moon) and weight downwards (from Moon), which balance. Plus an unbalanced friction force forwards (from Moon on the tyres). I...
  27. A

    Calculating Terminal Velocity for a Falling Object with Air Resistance

    Homework Statement An egg of mass 0.10 kg is dropped from rest at a height h. It is known that the egg dropped experiences a force due to air resistance of the form F = -kv, where v is the velocity of the egg and k is a constant of proportionality equal to 0.01781 N*s/m. What is the terminal...
  28. S

    How Do You Calculate Terminal Velocity Involving Drag?

    Hello PF, I have once simple (well, not so simple for me) question. I'm trying to derive an equation for the velocity of a falling body with accordance to terminal velocity. The equation incorporates drag proportional to the speed. m*dv/dt=mg-bv and mg/b=terminal velocity vt So the steps...
  29. G

    Terminal Velocity Given Acceleration at Instantaneous Velocity

    Homework Statement This is a repost of a homework like question. The previous thread I did not understand. In the assumption that drag is proportional to velocity, and when v = 20 m/s, a = 7.35 m/s^2, find the terminal velocity. Homework Equations The thread stated that the equation most...
  30. J

    Terminal Velocity of rain drops

    Please, explain the concept of terminal velocity on the help of rain drops... Is there is any retardation when rain falling to the ground.?
  31. M

    Drag - Terminal Velocity of a solid sphere.

    Homework Statement A solid sphere - 20mm in diameter, σ (specific gravity) = 1.3 dropped in water μ=1*10^-3 and ρ=1000 determine the terminal velocity for the sphere. (hint- guess the value for the drag coefficient then iterate) Homework Equations Fd=(1/2)*Cd*ρ*(U^2)*A...
  32. M

    Finding Terminal Velocity given Mass and magnitude

    I'm in physics 1 in college and reviewing for an up comming exam, ran into this problem and can't seem to figure out how to solve it. A 70 kg skydiver experiences a drag force as a function of velocity (in m/s), opposite the direction of motion, whose magnitude is given Fd(v)=0.19v^2...
  33. D

    Orbital mechanics terminal velocity vectors

    For a given space triangle, derive expressions for the terminal velocity vectors ##\mathbf{v}_1## and ##\mathbf{v}_2## between points ##P_1## and ##P_2## in terms of the unit vectors ##\mathbf{u}_1##, ##\mathbf{u}_2## and ##\mathbf{u}_c##. I know that ##\sin\left(\frac{\alpha}{2}\right) =...
  34. S

    Terminal Velocity: Solving for D

    Homework Statement A man 50.0kg has a terminal velocity of 42m/s. What value of D is required to make this possible? Homework Equations V(terminal velocity) = (mg/D)^1/2 The Attempt at a Solution D = (50kg*9.8m/s^2)/(42m/s)^2) = 0.28kg/m The book's answer is 44kg/m. Is the...
  35. J

    Question about Terminal Velocity Lab- without motion sensor

    Hello, We are doing a lab studying terminal velocity. Unfortunately we do not have a motion sensor, so we are dropping coffee filters at a certain height (both scrunched and flat- while increasing their numbers), and noting their final speeds. The thing I don't quite understand is whether...
  36. R

    Finding ratio of smaller terminal velocity to larger terminal velocity

    The terminal speed of a sky diver is 188 km/h in the spread-eagle position and 320 km/h in the nosedive position. Assuming that the diver's drag coefficient C does not change from one position to the other, find the ratio of the effective cross-sectional area A in the slower position to that in...
  37. Y

    How do you find terminal velocity?

    So I have a limited knowledge of physics, and so every article i have attempted to read contains to much technical jargon for me to understand. Can you please explain how, if given say a sphere, what measurements would need to be known? How would I go about calculating terminal velocity? Also...
  38. Hardik Batra

    Terminal Velocity: What is it?

    I want to know about terminal velocity. As my point of view, when air resistance and force(=mg) become same then the object moving downward has constant velocity. This is right? If right then v = (initial velocity)v + g*t; becomes v = g*t; then velocity increases by time !
  39. C

    Falling bodies and terminal velocity

    Is it correct to assume that two objects, with different masses, dropped from the same height at the same time will fall at the same rate until one of the objects reaches its terminal velocity? What are the applicable equation(s) used to calculate this?
  40. B

    Terminal Velocity of a Ball Given Velocity and Acceleration

    Homework Statement A steel ball is dropped from a great height. When its velocity is 20m/s its acceleration is 7.35 m/s^2. What is it's terminal velocity? Homework Equations V - V_o = at F = ma (Air resistance isn't given, so I don't think drag force can be used.) The Attempt at a...
  41. N

    Question: How does mass affect terminal velocity when a drag force is present?

    If two people of different masses say 50kg and 100kg were to suddenly jump off a building , why would the person with more mass attain a higher terminal velocity? I thought mass was irrelevant. I missed 1 lesson on this in class but this part I don't understand properly. If they were the same...
  42. A

    Magnitude of frictional force during terminal velocity

    Homework Statement A parachutist, after jumping from the plane, is accelerating down with average acceleration of 1.6 m/s2 (relative to the ground). What is the force of friction slowing his motion is mass of the parachutist with his equipment is 124 kg? What is the frictional force when the...
  43. M

    Solve DE for approaching terminal velocity

    Homework Statement I'm trying to find the function, that describes the velocity approaching to a terminal velocity.Homework Equations F_{net}=mg-\frac{1}{2}\rho v^2 AC_dThe Attempt at a Solution F=ma a=F/m \dot{v}=F/m=g-\frac{1}{2m}\rho v^2 AC_d \dot{v}=g-kv^2 \dot{v}+kv^2=g (k and g are...
  44. M

    Impact Speed vs Terminal Velocity

    What's the difference between impact speed and terminal velocity? I'm reading a book that gives a shortcut about how to calculate "The speed at impact in the y-direction when falling from rest" and it gives the eguation vt=9.8t.
  45. T

    Find velocity of a moment before terminal velocity is reached?

    Homework Statement Given g = 9.8 m/s 2 . A sky diver of mass 69 kg jumps from a slowly moving aircraft and eventually reachesher terminal velocity 56 m/s. What was (the magnitude of) her acceleration at the moment her velocity was only v1 = 39 m/s (directed vertically down)? Answer in...
  46. L

    Terminal Velocity and Millikan's Oil Drop Experiment

    Homework Statement Suppose I drop a ball from high enough in the sky that, at some point, it reaches terminal velocity. At this point, the ball is no longer accelerating. It is traveling at a constant velocity. Does this mean that at terminal velocity, the force of gravity on the ball is...
  47. M

    Terminal Velocity & Acceleration Question

    Homework Statement Hi there. I have previously asked questions on here and found it very helpful so would be grateful if someone could maybe help me again? I am currently studying for my Physics P2 GCSE unit and came across this question on the topic of Terminal Velocity. "Two identical...
  48. F

    Estimated terminal velocity significantly less than estimated impact velocity

    Homework Statement I am currently conducting an EEI in which I am looking at the effects of increased mass, surface area and air pressure on terminal velocity. In my experiment, I dropped a parachute of 0.36m^2 from a height of 3m with a mass of 0.01kg. My result was that it took 3.036...
  49. A

    Grabbing something at Terminal Velocity

    I know in Hollywood people fall a couple stories and grab onto a pole or something and survive, which most of the time doesn't seem too far fetched. But what if you were falling at terminal velocity and grabbed onto a horizontal pole? (The pole being a cantilever, and not flexible or anything at...
  50. B

    Relating terminal velocity, force of friction.

    I was working on problems for the MCAT and came across this below. After a few minutes working, I had couldn't come up with the solution. Usually the answer clears up any questions I have, but I'm having trouble figuring out how the force due to gravity matches the force of friction. I thought...
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