Falling Definition and 1000 Threads

In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it. In the context of general relativity, where gravitation is reduced to a space-time curvature, a body in free fall has no force acting on it.
An object in the technical sense of the term "free fall" may not necessarily be falling down in the usual sense of the term. An object moving upwards might not normally be considered to be falling, but if it is subject to only the force of gravity, it is said to be in free fall. The Moon is thus in free fall around the Earth, though its orbital speed keeps it in very far orbit from the Earth's surface.
In a roughly uniform gravitational field, in the absence of any other forces, gravitation acts on each part of the body roughly equally. When there is no normal force exerted between a body (e.g. an astronaut in orbit) and its surrounding objects, it will result in the sensation of weightlessness, a condition that also occurs when the gravitational field is weak (such as when far away from any source of gravity).
The term "free fall" is often used more loosely than in the strict sense defined above. Thus, falling through an atmosphere without a deployed parachute, or lifting device, is also often referred to as free fall. The aerodynamic drag forces in such situations prevent them from producing full weightlessness, and thus a skydiver's "free fall" after reaching terminal velocity produces the sensation of the body's weight being supported on a cushion of air.

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  1. N

    Mass on a spring inside a box falling under gravity

    Homework Statement A mass m is attached to a spring(massless) that is located inside a massless box. The box is falling under gravity. When the box starts to fall the spring is in it's equilibrium position and the box sticks to the ground when it hits it. -The box is a distance H from the...
  2. C

    Falling Velocity Relative to Weight

    Homework Statement A wooden rod of negligible mass and length 80.0 cm is pivoted about a horizontal axis through its center. A white rat with mass 0.490 kg clings to one end of the stick, and a mouse with mass 0.240 kg clings to the other end. The system is released from rest with the rod...
  3. D

    Differential free falling bodies

    (i) how you solved this problem, An object of mass 10 kg is dropped from a great height. (a) If the object is subjected to air resistance equivalent to 10 times the instantaneous velocity, find the velocity. (b) How far does the object drop after 5 sec? (ii) what you got as a solution...
  4. P

    Potential difference of falling charge particle

    Homework Statement A particle of mass 7*10e-5 kg and charge 1e-6 C from point A to point B a distance of 3 m in the Earth's gravitational field. The kinetic energy of the particle decreases by 5.3mJ during this movement. The acceleration of gravity is 9.8 m/s^2. What is the potential...
  5. L

    Solving a Physics Problem: Falling Ball from Tabletop

    Homework Statement A ball rolls horizontally off the edge of a tabletop that is 1.40 m high. It strikes the floor at a point 1.56 m horizontally away from the table edge. (Neglect air resistance.) (a) How long was the ball in the air? _____ s (b) What was its speed at the instant it...
  6. R

    Free Fall: Heavier Object Hits Ground First?

    Hi guys, quick and simple question! If you allow 2 objects with different weights but exact same shape to free-fall in the presence of air resistance will they hit the ground at the same time (assuming terminal velocity isn't reached by either object). I'm pretty sure the heavier object hits...
  7. D

    What is the Pressure of Falling Sand on a Sticky Surface?

    Homework Statement Grains of sand of mass 2.90x10^-3 g each, fall from a height of 0.5 m on a sticky surface at a rate of 45 grains per second per cm^2. What pressure does this shower of sand exert on the surface, assuming that air resistance can be neglected? Homework Equations...
  8. P

    Free Falling Objects: Find Time for Mailbag to Reach Ground

    Homework Statement The height of a helicopter above the ground is given by h = 3.00t^2, where h is in meters and t is in seconds. After 2.00s the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground Homework Equations Xf = Xi + VxT + .5at^2...
  9. T

    How Fast Will the Flower Pot Hit the Ground?

    As you look out of your dorm window, a flower pot suddenly falls past. The pot is visible for a time t, and the vertical length of your window is Lw. Take down to be the positive direction, so that downward velocities are positive and the acceleration due to gravity is the positive quantity g...
  10. B

    Water falling = how much power?

    Water flows over a section of a waterfall at the rate of 3.2 104 kg/s and falls 33 m. How much power is generated by the falling water? watts i tried to use the power equation but I am just not sure how the numbers relate. help please?
  11. H

    Can spinning reference frames mimic gravitational fields?

    Hey everyone, THIS IS NOT A HOMEWORK QUESTION. This is a question I think I know the answer to but I want to see what you get to check my answer. Here is the setting. You take an object up into the atmosphere. Far enough away so that the acceleration do to gravity of the Earth is 1 m/s^2...
  12. J

    Falling object - relating distance interval to time interval

    Homework Statement An object falls from the top of a 103.6m high building. The vertical distance between two consecutive windows A and B is 4.0m. The first window/storey is also 4m from the top of the building. The object reaches window B 0.1s after it has reached window A. Which...
  13. T

    A Square Loop of Wire falling through a Magnetic Field

    Homework Statement A vertical square loop of copper wire with sides of length 100 mm is falling from a region where the magnetic field is horizontal and of magnitude 1.2 T into a region where the field is zero, as shown in the diagram below. The diameter of the copper wire is 1 mm. [The...
  14. J

    Particle Falling g=1m/s^2 how much time does it take to fall?

    Homework Statement A particle falls freely through a distance of 1.00 m starting from rest. Assume resume that g = 10 m/s^2. How much time does it take to fall? (4E-1) Homework Equations I think a=vf-vi/t The Attempt at a Solution I've tried 10m/s^2=1/10m/s-0/t And tried to...
  15. P

    How Long Does It Take for a Falling Water Drop to Freeze at -20°C?

    Hi all, I have a heat transfer problem. In this problem, a water drop (assume sphere) is falling from a very high building. The outside temperature is below zero say -20 degree centigrade. How much time will it take to freeze? I am not able to understand how to model this problem. Which...
  16. 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
  17. W

    What Is the Stone’s Speed at 96,000 km From Earth?

    I have a bunch of ideas how to solve this problem, but I cannot figure out which one is right... A stone is released from rest at the Moon’s orbit and falls towards the Earth. What is the stone’s speed when it is 96,000 km from the center of the Earth? Thanks, Adam
  18. H

    Electric Charge of Water droplet falling

    Homework Statement A charged water droplet of radius 0.02 mm remains stationary in air. If the electric field of the Earth is 100 N/C downward,what is the charge on the water droplet? By comparison with its neutral state, how many electrons must the water droplet have gained or lost? [...
  19. M

    Showing that energy of a falling object remains constant

    I got this question on a sample test but I don't know how they want me to answer it Q.) Show that for a falling body, the total amount of energy is constant at any point I suppose I could state the potential energy then draw a graph of how the potential energy is converted into velocity. Is...
  20. P

    Why does a falling object hit harder despite having the same force?

    I posed this question to my teacher: I have a 2 kg object and it sits at rest on the floor. The force is mass * acceleration, so it's about 20 N. Now I drop the ball from, say, 20 feet above the ground. Same mass, same acceleration, so it has the same force, 20 N; but we know the object hits...
  21. J

    Catching a Falling Can: Solving for Acceleration

    Homework Statement "A friend leans out of an upper window of an apartment building and drops a canned beverage of your choice to you on the sidewalk below. Unfortunately, you aren't directly beneath the window; instead, you are standing where the angle to your friend is 75 degrees above...
  22. K

    Horizontal and Vertical components of falling objects

    Seen as i had difficulty understanding this little topic and with my AS level exam soon, i figured i should find somewhere to ask without having to wait while class, so here goes... I had some questions to do (but this isn't about homework!) i couldn't seem to be able to get the right answer...
  23. R

    What is the terminal velocity of mass falling toward earth?

    Assume no atmosphere; no friction; no extraneous factors. What is the terminal velocity of a mass that falls from the edge of Earth's gravity well to Earth's surface? Thank you in advance for your answer. Peace rwj
  24. A

    Calculating Final Speed & Energy of 0.1 Solar Mass Falling into the Sun

    Homework Statement (b) If an object of 0.1 Solar masses fell into the Sun (starting at rest at infinity) calculate what its final speed and energy would be. Mass of the Sun = 1.99 x 10^{30} kg Radius of the Sun = 6.96 x 10^8 m The Attempt at a Solution Having done the rest of...
  25. T

    Acceleration of a falling tower

    This is problem 67 in Chapter 10 of Halliday/Resnick/Walker 8th Edition. This is one of their three star (= hard) problems. I can get the beginning but then get stuck. A cylindrical chimney of height L=55m falls over. Treat it as a thin rod. Get the radial acceleration and tangential...
  26. P

    Finding velocity of a falling object

    Homework Statement When Mongol drops his ball off the Hasselbluff Mountain Viewpoint, its height above the ground at time t is given by h = 64 - 1/2gt2. How long will the ball take to hit the ground? How fast is the ball going the instant before it hits the ground? Homework Equations I...
  27. J

    Falling egg question (with energy equations)

    An egg of mass 5.8*10^-2 is dropped from a height of 1.5m onto a floor. Assuming air resistance is negligable, calculate for the egg: a) loss of potential energy. b) the kinetic enrgy just before impact. c) the speed just before impact d) the momentum just before impact. So far i have...
  28. J

    Terminal velocity when falling through the atmosphere

    Dear all, I have been working my way through the Oxford University physics test sample paper http://www.physics.ox.ac.uk/admissions/combined-sample.pdf" and I have come across this question: A sky-diver jumps out of an aeroplane. Which of the following statements is true after she reaches...
  29. A

    What is the Vertical Acceleration of a Falling Tennis Ball?

    Homework Statement A flash photograph of two tennis balls released simultaneously is taken. One is projected horizontally, and the other one is dropped from rest. The light flashes occur ever 0.2 seconds, and each box represents a distance of 0.4 s (they gave a graph...I can't get it on the...
  30. fsteveb

    Researching ball falling into fluids

    I want to write a opengl (graphical) representation of a non-deformable ball or other shape in general being dropped onto a liquid surface. The surface will consist of a grid with surface maps. So I need to calculate I assume the wave equation in response to the object impact. Once I get the...
  31. D

    What is the Velocity of a Falling Body with Friction in Freefall?

    a small body, with the mass of M is dropped from an infinite height falling freefall, the air's friction on the body is defined by ==>f=-kv^2, k=const. find the velocity after an infinite amount of time. using Newtons 2nd law, F=ma=mg-kv^2 a=g-(kv^2)/m now, how do i find the velocity...
  32. nicksauce

    Black Hole Event Horizon and the Observable Universe

    I was watching a NOVA program, and they claimed that if you were falling into a black hole, when you crossed the event horizon you would be vaporized by the intense light that's built up at the surface that hasn't been able to escape the BH. This seems plausible, I suppose, but I have never...
  33. S

    Impact Force after falling of a chair

    Hi, Hopefully somewone will know the calculation to find out the impact force for one person sitting on a chair and falling backwards with a full deaceleraton to a hard floor, what would the impact force be to the base of he head when stricking the floor. Chair is a chair with a bottom and...
  34. T

    How can the dynamics of falling balls be analyzed using equations of motion?

    Homework Statement http://members.shaw.ca/code/balls.JPG" Homework Equations I'm not sure what equations to use here, or even wether or not I need to use calc. Unfortunately we just started dynamics and most students don't know how to integrate yet (including me) v = dx/dt a =...
  35. T

    Verifying the Accuracy of a Gun Aimed at a Falling Target

    Homework Statement A gun is aimed directly at a can, which is simultaneously released when the gun is fired. This gun won't miss as long as the initial speed of the bullet is sufficient to reach the falling target before the target hits the floor. Verify this statement. Homework...
  36. S

    The instantaneous velocity of a freely falling object

    What is the instantaneous velocity of a freely falling object 10 s after it is released from a position of rest? What is its average velocity during this 10 s interval? How far will it fall during this time? I had asked a few friends for help and I keep getting mixed answers. v = gt 98m/s...
  37. T

    What are the forces acting on a ball falling through a liquid?

    The Attempt at a Solution I think the first part is just 9.8 but I have no idea on the rest of the problem (this is due tomorrow need help)
  38. J

    Ball falling on to parabolic track

    1. A 50 g ball is released from rest 1.0 m above the bottom of the track. It rolls down a straight 30 degree segment, then back up a parabolic segment whose shape is given by y = 1/4x^2, where x and y are in m. There is a picture shown too, but I can't figure out how to get it in the post...
  39. W

    Solve Free Falling Motion Homework: Traveled in 3rd Sec of Fall

    Homework Statement An object is released from a height of 50m. How far has the object traveled during the 3rd second of fall?Homework Equations d = Vi*T + 1/2at^2 Doesn't work though - answer provided is 24.5m. The Attempt at a Solution I did a simple distance at 3 seconds with 9.81 m/s^2 as...
  40. B

    How can I calculate the speed of the other end of a falling rotating stick?

    Homework Statement A stick of length 0.8 m is held vertically with one end on the floor and is then allowed to fall. Find the speed of the other end when it hits the floor, assuming that the end on the floor does not slip. Homework Equations w=sqrt(3g/2h) Should I use I=.5ML^2 or...
  41. J

    Using Impulse-Momentum to Find Time of Falling Object

    Homework Statement Use the impulse-momentum theorem to find how long a falling object takes to increase its speed from 5.50 to 9.00 . Homework Equations deltaP = impulse P = momentum (m*v) impulse = J (integral from ti to tf) The Attempt at a Solution 3.5 seconds, though, I knew...
  42. S

    Ball and Runner: Catching at the Bottom of a Building

    Homework Statement A ball is thrown from top of a 25m tall building. The balls initail speed is 12m/s. At the same instant a person is running on the ground at the distance of 31m from the building. What must be the avg speed of the person if he is to catch the ball at the bottem of the...
  43. C

    Disintegration of a falling drop of liquid

    What are the variables that determine the maximum diameter of a drop of liquid that will not disintegrate while falling through a gas (e.g. raindrop falling in air)?
  44. C

    Which Animal Would Sustain More Injury from a Fall: Turtle or Beetle?

    If a turtle and beetle fall from the same height, which would sustain more injury? Assume that both the turtle and beetle are geometrically similar. The amount of force of which the creatures reach the ground would be the measured parameter, right? So, including air resistance in the equation...
  45. S

    Solving Free Falling Objects Problem

    Homework Statement A girl throws her set of keys to her friend upward who is in a window 3.90m above. the keys are caught later at 1.30s by the friends hand. Homework Equations a. With what initial velocity were the keys thrown? b. What was the velocity of the keys just before they...
  46. S

    Work done by gravity on falling object

    Homework Statement A 3000 kg space vehicle, initially at rest, falls vertically from a height of 3500 km above the Earth's surface. Determine how much work is done by the force of gravity in bringing the vehicle to the Earth's surface. Homework Equations Gravitational potential...
  47. B

    Finding the Speed of a Falling Elevator with a Spring and Frictional Force

    Homework Statement In a "worst-case" design scenario, a 2000-kg elevator with broken cables is falling at 4.00 m/s when it first contacts a cushioning spring at the bottom of the shaft. The spring is supposed to stop the elevator, compressing 2.00 m as it does so. During the motion a safety...
  48. L

    Two pieces, side by side, are falling down, into vacuum, by the only

    Two pieces, side by side, are falling down, into vacuum, by the only attraction of a planet gravity. One is 1.000 Tons weight and the other piece is 0,001 Tons weight. Wich one is going to hit the planet´s ground first?
  49. B

    Measurement of g with a free falling plummet

    [b]1. I recently had a lab on free falling and have all the data and percentage amounts from the data sheet, and Position vs. Time. I'm having a problem creating the slope for the velocity vs. Time. Do I use two different points or just one point? I used to different tangent lines...
  50. science_rules

    Understanding horizontal and vertical components of a falling object

    I want to understand this: In the case of a dropped object, the horizontal component of the velocity with which the object hits the ground is not the same thing as the horizontal velocity itself, am i right? The horizontal component of the velocity when the object hits the ground means the...
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