What is Fall: Definition and 922 Discussions

Autumn, also known as fall in North American English, is one of the four temperate seasons. Outside the tropics, autumn marks the transition from summer to winter, in September (Northern Hemisphere) or March (Southern Hemisphere), when the duration of daylight becomes noticeably shorter and the temperature cools considerably. Day length decreases and night length increases as the season progresses until the Winter Solstice in December (Northern Hemisphere) and June (Southern Hemisphere). One of its main features in temperate climates is the shedding of leaves from deciduous trees.
Some cultures regard the autumnal equinox as "mid-autumn", while others with a longer temperature lag treat the equinox as the start of autumn. In the English-speaking world, autumn traditionally began with Lammas Day and ended around Hallowe'en, the approximate mid-points between midsummer, the autumnal equinox, and midwinter. Meteorologists (and Australia and most of the temperate countries in the southern hemisphere) use a definition based on Gregorian calendar months, with autumn being September, October, and November in the northern hemisphere, and March, April, and May in the southern hemisphere.
In North America, autumn traditionally starts with the September equinox (21 to 24 September) and ends with the winter solstice (21 or 22 December). Popular culture in the United States associates Labor Day, the first Monday in September, as the end of summer and the start of autumn; certain summer traditions, such as wearing white, are discouraged after that date. As daytime and nighttime temperatures decrease, trees change colour and then shed their leaves. In traditional East Asian solar term, autumn starts on or around 8 August and ends on or about 7 November. In Ireland, the autumn months according to the national meteorological service, Met Éireann, are September, October and November. However, according to the Irish Calendar, which is based on ancient Gaelic traditions, autumn lasts throughout the months of August, September and October, or possibly a few days later, depending on tradition. In the Irish language, September is known as Meán Fómhair ("middle of autumn") and October as Deireadh Fómhair ("end of autumn"). Persians celebrate the beginning of the autumn as Mehregan to honor Mithra (Mehr).

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  1. T

    Creating friction in a fall arrest device

    Hey Everyone, I'm currently looking at designing a device that would allow people to escape from working at heights quickly and safely in the event of an emergency (up to 33 m) I know there are some products on the market already but since I don't have a great deal of experience with them...
  2. J

    Free fall w/ Air Resistance

    A ball of mass m is released from rest at x=0. Air resistance is expressed as R = kv2 , where k is a positive constant and v denotes velocity. Derive an expression for the speed in terms of the distance x that it has fallen. Identify the terminal v. I know I have to start with ma = mg -...
  3. B

    Kinematics: Rocket/Free Fall Problem

    Homework Statement A one stage booster rocket has a Xo of 0m and a Vo of 0 m/s. The rocket takes off with a constant acceleration until 5 seconds when the boosters turn off and goes into free fall. The rocket is set to explode the instant it hits it's max height. The max height is 1200m...
  4. S

    Does this potential fall semester schedule sound too intense?

    This is my first post on here, so I apologize in advance if I'm in the wrong section or something. I was thinking about having this as my schedule for the fall semester. -Analysis I -Discrete Mathematics -General Physics I -Data Structures I'm not sure if I'm being overly ambitious...
  5. S

    Spring force with free fall problem

    Homework Statement Consider the system below. The 2.50 kg mass compresses the spring (k = 805 N/m) a distance of 0.230 m from equilibrium. The mass is then released from rest. It slides a total distance of 1.20 m on the table top where it feels a force of kinetic friction of 5.60 N before it...
  6. R

    Time to Hit the Ground for Thrown Rock?

    Homework Statement A rock is thrown vertically upward with a speed of 17.0 from the roof of a building that is 60.0 above the ground. Assume free fall. In how many seconds after being thrown does the rock strike the ground? Homework Equations I used v^2 = vinitial^2 + 2a(y - yinitial)...
  7. T

    What is a Geomagnetic Storm and How Does it Affect Earth?

    can somebody explain to me what is geomagnetic that recently run down to earth? i really want to know.
  8. B

    Admissions Spring GRE, Fall admissions. Will I get my scores in time?

    So I'm studying for the physics GRE and plan on taking it this April. While I understand the deadline for admissions to most universities is right up until the semester begins, I also understand it is a first come, first serve deal. Are most slots going to be filled by May, when the scores...
  9. M

    Free fall with air resistance, must find velocity

    Homework Statement The problem is to find the velocity as a function of time, given the following; the object is in free fall and its initial velocity is zero. The formula given for the air resistance is: a = g - kv, where g is acceleration d/t gravity, k is a constant, and v is velocity...
  10. L

    Finding Terminal Velocity of a Balloon in Free Fall

    Hi everyone, I am doing a lab report about free fall, but I have to find the terminal velocity for the balloon, but I don't know if I can use the formula velocity = Distance / Time because I have 10 measures from free fall ( 0.2 m - 2 m) , and I have the time that it took to hit the ground...
  11. L

    Exploring Different Equations for Free Fall Drop

    [b]1. Wondering if there are any different equations out there for free fall drop. [b]2. The only one I received was H=1/2gt^2 [b]3. I don't know if there are any others, someone said ΔX=ViTf+1/2aTf^2, but I don't think that's for free fall?
  12. A

    The Slowest fall / simple aerodynamics

    Homework Statement The problem is to construct a model out of ordinary materials such as paper, blotting paper, foil, tights and so on, that is supposed to fall along about 3 metre long runner with as longest time as possible. (with the inspirations like maple seed)The Attempt at a Solution I...
  13. A

    Why doesn't the moon fall down?

    I understand that the moon doesn't fall down because it is in an orbit around the Earth. Is this orbit created by warped space due to the mass of the earth?
  14. S

    How far must the mass fall to give a rotational rate of 3 rev/s?

    Homework Statement A whee and axle having a total moment of inertia of .0002 kg*m^2 is caused to rotate about a horizontal axis by means of an 800g mass attached to a cord wrapped around the axle. The radius of the axle is 2 cm. Starting from rest, how far must the mass fall to give the wheel...
  15. S

    Force of an Object in Free Fall: Mass x Gravity

    Does a falling object hit the ground with a force of its mass times "a" of gravity? Hi, When an object is falling through the air and in free fall with no air resistance, the applied force is the net force on the object: the object's mass times the acceleration due to gravity (or...
  16. G

    Time for object to fall length of 10m rope, assuming g=10m/s

    I'm still struggling with spacetime curvature. I want to know about the spacetime intervals in the following scenario: An apple is cut loose from a tree, but is still attached by an unstretchable rope that is measured to be 10 meters by the tree observer. (I'm ignoring all but relativistic...
  17. N

    Physics puzzle ratios of two times which it take an object to fall down.

    Homework Statement What is the ratio between times for the aliens to hit the floor. you have two spheres of equal density throughout. One has a radius R and the other 1/2R. An alien falls down one and takes time T, the other it falls down in time t. In the second on, time t, half of the mass...
  18. M

    The First Snow Fall of the Season

    "Yes! The first snowfall of the year" - someone, somewhere at least once a day Is this statement true?
  19. T

    Egg Drop Project: Prepping the Container for a Successful Fall

    I have an egg drop project, in which we make a container on the ground that can cushion the fall of the egg. The limits are: 8 cm height max, and 45 x 45 cm box max area and the egg must not break even if it bounces out after hitting the container. It'll be dropped first from a height of 2...
  20. G

    Is it scientifically feasible to create a boot that could soften a 30 m fall?

    It would probably require some sort of leg attachment to relieve the stress on the knees and ankles. Is it within the realm of possibility?
  21. T

    Free fall without a lot of info.

    Homework Statement A ball is thrown horizontally at 16m/s from a clifftop 65m above the sea level. Find the time to land Homework Equations distance = Vi*t + at^2/2 The Attempt at a Solution I separated x and y components. And tried to plug them in this formula. I thought...
  22. M

    Why does an object fall in the same time as it takes to reach a peak

    Homework Statement A kangaroo jumps a height of 2.8m. How long was it in the air? Homework Equations v=v0+at x=x0+v0t+(1/2)at^2 v^2=v0^2+2aΔx The Attempt at a Solution -2.8 = -4.9t^2 .57 = t^2 t = .76 s (down) 0 = v0^2+2(9.8)(2.8) 54.88 = v0^2 v0 = 7.408 0 = 7.408-9.8t t = .76 (up) t...
  23. N

    Wgat would a light clock measure in free fall?

    Wgat would a "light clock" measure in free fall? I've read in a couple of different books that the similarities between acceleration from gravity and rockets or whatever is only local. Both books said one of the reasons is because with acceleration from gravity two objects in free fall starting...
  24. V

    Free Fall Equations: Velocity and Air Resistance Effects Explained

    Homework Statement A particle of mass m falls from rest from height h above the ground. The retarding force per unit mass due to air resistance is kv^2 where k is a constant and v is the velocity of the particle a) write and simplify the equation of motion for the particle b) find an...
  25. S

    Does a Ball Dropped from a Rising Hot Air Balloon Continue Ascending?

    Hi, I was watching a hot air balloon show, and one of the demonstrations was someone dropping a ball out of a rising hot air balloon. If a hot air balloon is rising at let's say 19.6m/s, and you drop a ball directly down, will the ball continue to rise for two seconds because it has an...
  26. P

    How much does a body weight in free fall?

    Homework Statement Well, that's all, my mid-term exam came a question that asked me: if a body with mass of 50 kg was weighed on a scale that is inside an elevator in free fall, how much will it weight? I supposed that the same it would weight on the surface, since gravity never stops...
  27. N

    Kinematics/free fall objects help.

    In my honors course we are covering kinematics concepts. There was this problem which stumbled me but then I figured out what I did wrong. I just want to make sure my concept was right. Here is the problem... A diver springs upward with an intial speed of 1.8 m/s from a board that is 3 meters...
  28. S

    Why can't we see anything fall into the black hole?

    Flicking through quite a few topics here, I have seen that everyone says we can't get to see anything fall into the black hole as it would take ∞ time for us. Now, I'm a bit bugged here. Can someone explain me why it is like that. Also, haven't we seen stars fall into black holes through...
  29. M

    Creating a Drag Shield for a free fall object

    Would anyone know how to determine the area that a drag shield would have to be to allow an object above not to experience no more then .001 Gs? The drag shield that I was thinking about is just a flat sheet attached to the bottom of the top object by a string. Would this even be possible?
  30. Gannet

    According to our weather person, Fall starts on 9/23/11, How?

    I assume this is the right forum to ask this question Based on what I think I know, the Earth completes one full orbit of the Sun in approximately 365.25. Every four years we have a Leap year that adds one day. This I understand. What confuses me is how can Fall begin more than 24 hours...
  31. K

    BH fall time = pi*m. What is external time?

    Problem 17.3 in the "problem book in relativity and gravitation" states: "Show that once a rocket ship crosses the gravitational radius (horizon) of a Schwarzschild black hole, it will reach r=0 in a proper time tau less than or equal to pi*m, no matter how the engines are fired." My...
  32. C

    Finding initial velocity in free fall with given meters.

    Homework Statement A juggler throws a ball just so it reaches the ceiling at 3.0 meters. (3m above hand) How do I solve for initial velocity? Homework Equations The Attempt at a Solution
  33. Evo

    What Are Men Really Wearing This Fall?

    Male Fall Fashion...really? Ok, I want to know how many men want to wear this shirt. Do these guys look mad because they're wearing the same outfit, or because they had to wear the shirt. Are those wild animals?
  34. R

    Free Fall & Gravity: Feelings & Differences

    does a person feel weightlessness or any differences when he make a free fall under gravity of different values say 10m/s^2 or 25 m/s^2. Also it is said a person float in empty space is similar to a free fall. Free fall means it speed accelerates, then it would reach an infinite speed if it...
  35. Simfish

    Has anyone here gone to the AGU Fall Meeting?

    http://www.facebook.com/AGUFallMeeting?sk=wall&filter=2#!/AGUFallMeeting?sk=wall Just wondering. I'd like to know how it's like and if students are allowed.
  36. pankaj66866

    Why Don't the planets fall into sun.

    May be this question has been asked multiple times here i was just unable to search it by topic or search term. The Question is if every thing is falling towards the sun (i.e planets). Why planets are not falling towards sun in a spiral fashion and ultimately crash into sun ? This may be...
  37. AlexChandler

    Need advice on my Fall schedule

    Hello, I am a math and physics double major and a junior at Michigan State University. I have already taken introductory physics, the first semster of classical mechanics, a course in thermodynamics and modern physics, and linear algebra (along with the basic calculus and diff eq courses) I...
  38. M

    Courses Aero Eng. & Math: Exploring Courses for Fall Semester

    I want to major in aero. engineering and mathematics. Over fall semester I will be taking Object-Oriented Programming, Calc/Analytic Geom I, and General Physics I lecture and lab. I really enjoy math and want to take any courses that will improve my math skills that is why I am taking a...
  39. T

    Is this schedule for the fall too heavy? (

    Is this schedule for the fall too heavy? :(( -Intermediate Mechanics I -Intermediate E&M I -Linear Algebra -Fundamental Mathematics (intro proof class for math majors taken after Calc III) -General education course (irrelevant) Total: 15 hours It's...
  40. C

    Is my Fall schedule too demanding?

    Hey all, I'm a CCC student right now pursuing a career in Aerospace Engineering. Right now my GPA is a 3.7 and I only intend for it to go higher. It would probably be a 3.8-3.9 if my Chem teacher didn't screw me over last semester, but that's besides the point. :P This fall I'm taking...
  41. M

    Programs Chances and Preparation for Fall 2012 Math PhD Program

    Would I be able to get into any PhD Program for applied math? Would you please recommend some PhD and/or masters (with funding) programs to apply to? I'll be graduating in Spring 2012 and unfortunately, my undergrad institution only funds for an extra semester, so my only choice is to apply to...
  42. Ryan_m_b

    The fall of an Empire hopefully

    The Murdoch empire has had to http://www.bbc.co.uk/news/business-14142307" is this the end of the company that bought us the appalling Fox news and authorised despicable journalist tactics?
  43. S

    TIME of FREE FALL, variable g

    Homework Statement when g = constant , time = v / g if g varies how do I get t ? One electron is at rest at r0, 3600 km from surface of Earth (r), 10.000 km from center. g(r) = 9.8 m/s^2 , g(r0) = 4, Δ PE = 2.25 x 10^7 1) If it fell in a vacuum, after how many seconds...
  44. D

    Please help me. topic: ( motion with constant acceleration : free fall )

    Homework Statement A scaffolding is rising at 1.0 m/s when at a height of 50.0 m , then the man on the scaffolding drop a can. determine: a. the time needed for the can to reach the ground . b. what is the final velocity ?Homework Equations note: g=-9.8 m/s the letter o in the equation...
  45. Mentallic

    Dense Helium Balloons: Will They Rise or Fall?

    I just need some clarification on this. It is well known that a balloon filled with helium will rise since helium is less dense than air, but what if the balloon were to stay the same weight, but the elastic itself has become much stronger, thus we could concentrate the helium even more...
  46. pairofstrings

    What type of category of systems does a computer PC fall under?

    Is it a linear system? Casual system? Please explain why and how.
  47. B

    Free Fall: Understanding Conditions & Air Resistance

    Hello, I was wondering under what conditions does free fall need to comply to in order to take effect? I am pretty certain that for an object to be in free fall it needs to be void of any friction, but what about air resistance? Or is air resistance a form of friction? Thank you in advance.
  48. 3

    Solving the Last 3/4 of a Second Fall: Can You Do It in 3 Minutes?

    The released last seconds of the fall of a body of the road 3 / 4 of fame is. According to this time how many seconds of falling down? please solve this so quickly . . . (in 3 minutes)
  49. M

    What do you think of this fall quarter schedule?

    So I am going to be a senior this fall double majoring it mathematics and economics right now my schedule is for the fall is: Topology (5 units) Game Theory (5 units) Poverty/Public Policy (5 units) and most likely going to be grading for vector calculus or number theory. I...
  50. T

    Summer getting too hard for you? Post your Fall Schedule to cool down

    Summer has started and I know a lot of college students have already made their schedule for fall. Post them here! I'll start... Engineering Mechanics Thermal Science Nuclear System Dynamics/Control Numerical Methods and Fortran Nuclear Engineering Lab I'm also considering adding...
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