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. D

    Finding Max Spring Compression for Firefighter Fall

    Homework Statement A 60.kg firefighter slides down a pole while a constant frictional force of 300N retards his motion. A horizontal 20.0kg platform is supported by a spring at the bottom of the pole to cushion the fall. The firefghter stars from rest 5.00m above the platform, and the spring...
  2. P

    Free Fall Rocket Acceleration Problem

    Homework Statement A student walks off the top of the CN Tower in Toronto, which has height 553m and falls freely. His initial velocity is zero. The Rocketeer arrives at the scene a time of 4.75 seconds later and dives off the top of the tower to save the student. The Rocketeer leaves the...
  3. C

    Cold Weather Convection: Does Warm Water Rise or Fall?

    Does warm water rise or fall in cold weather? I think it falls Does it have to do with convection??
  4. A

    Admissions Navigating Financial Aid: Tips for Applying in Fall 2007

    OK, I'll be applying for a couple of universities in the fall of 2007. Now what's more confusing then anything else and is driving me nuts is all the financial aid stuff. The websites say my deadline is February 1. February 1 of what, 2007 or 2008? If it's Feb 2007, then that's crazy. Since I...
  5. D

    Revisiting the Definition of Free Fall: Acceleration or Standing Still?

    If you are in free fall you would be standing still, with no acceleration right? So in a way you are decelerating(or accelerating in the opposite direction) in 9.8m\s^2, when you are standing on the earth, is that true? Or would you have to look at it otherwise? So free fall cannot be...
  6. L

    Finding final velocity from a fall

    I'm having trouble with this problem: So for this problem i used F=ma: 79g-88=79a a=8.6861m/s^2 this is the correct acceleration i believe and to find final velocity i used: Vf^2=Vi^2+2ad where d is displacement Vf^2=2(8.6861)(25) vf=20.85m/s I'm using utexas's webhw service, and the...
  7. J

    Why Don't Satellites Fall Into Earth? Exploring Gravity's Effects

    when a satalite orbits the Earth my text states that it is constantly falling into the Earth as it moves tangentially -- my question is why doesn't the speed of the object falling into the Earth increase radially since it is acted upon by the force of gravity, a force of gravity would cause an...
  8. B

    Exactly Why doesn't the moon fall and strike the earth?

    Is it because the moon is actually falling in free fall TOWARDS the Earth but it is moving in a circular path the same as the Earth's path??
  9. R

    How long does it take to fall to the center of the earth?

    Let's assume that there are no other forces acting besides the gravitational pull of the earth. If a body started falling from the surface how much time would it take before it reached the center of the earth? It seems like an easy problem, but so far I have had no luck. So far I have only...
  10. L

    Blocks stacked on an edge - max dist. b4 they fall?

    The question is "Two identical uniform bricks of length 18 cm are stacked over the edge of a horizontal surface with the maximum overhand possible without falling." |<-- 18 cm -->| +-------------+ | block 1 | +-------------+ +-------------+ | block 2 |...
  11. R

    Kinetic energy of free fall

    An airplane propeller is 2.08 m in length (from tip to tip) with mass 117 kg. The propeller is rotating at 2400 rev/min about an axis through its center. Its rotational kinetic energy is 1.33x10^6 J. If it were not rotating, how far would it have to drop in free fall to acquire the same...
  12. J

    Energy Transformation equation for a free fall

    One of the discussion questions in a lab I did which was basically a free falling object where the kinetic and potential energies were measured. It asks what is the energy transformation equation for a free fall (1-step transformation). Is it just: Total Energy = Potential gravitational energy...
  13. DaveC426913

    Book about explanations: what made the cylinder fall over?

    Years ago I read a book that explored what it means to people to satisfactorily "explain" something. There were 5 different levels of "doneness". I'm looking for that book. In a nutshell, the book explored a lecture hall experiment: - a cylinder was placed on a table at the front of the room...
  14. R

    Does a bullet fall at a greater force?

    okay my question is kinda stupid, and i know i totally sux at physics. if a bullet is shot upwards, will it fall at an equal or greater force? i know its decelerating as it is shot up, and it would be acclerating as it falls, and so wouldn't it fall at a greater force?
  15. U

    Solve Kinematics Problem Involving Free Fall Acceleration

    Hi, I have a kinematics problem involving free fall acceleration. I'm not sure how to do this so I was wondering if someone could please give me a hand. Thank you. Question: Water drips from the nozzle of a shower onto the floor 2m below. The drops fall at regular (equal) intervals of...
  16. Evo

    Fall Flavors: Caramel Apples and Chocolate Haystacks

    The frost is on the Pumpkin, it's that time of year. When the girls were little, we would always make caramel apples in October. The REAL kind where you melt the caramels, stick the wooden popsicle stick into the apple and then dunk it into the hot caramel. No using those pre-made apple...
  17. mbrmbrg

    Calculating Forces on a Block Against a Wall

    Block on Wall--Does it Fall? A 15 N horizontal force F pushes a block weighing 3.0 N against a vertical wall (Figure 6-25). The coefficient of static friction between the wall and the block is 0.71, and the coefficient of kinetic friction is 0.51. Assume that the block is not moving initially...
  18. L

    Help! I Need a Problem Involving Free Fall & Relative Velocity!

    I have to make up or find a problem that invovles free fall velocity AND relative velocity! Can anyone find/make up a problem for that? HELP!
  19. S

    Constant acceleration and free fall

    Hey, I've been having some problems with finding out the rocket's maximum altitude and was wondering if anyone could help. The question information is: A 200kg weather rocket is loaded with 100 kg of fuel and fired straight up. It accelerates upward at 34.0 for 31.0 , then runs out of fuel...
  20. Y

    Solve Weight & Free Fall on a Far-Away Planet - Astronaut Problem

    Hey guys, I'm confused about this problem - On a planet far, far away, an astronaut picks up a rock. The rock has a mass of 5.80 kg, and on this particular planet its weight is 40.0 N. If the astronaut exerts an upward force of 43.3 N on the rock, what is its acceleration? I thought you...
  21. T

    Box Mass and Friction: Calculating Time Before Fall

    A box of mass 12.5 kg rests on the flat floor of a truck. The coefficients of friction between the box and floor are mu_s = 0.190 and mu_k = 0.150 . The truck stops at a stop sign and then starts to move with an acceleration of 2.19 m/s^{2}. If the box is a distance 1.79 m from the rear of the...
  22. T

    Free Fall Q: Find Where Balls Cross Paths

    Here's the question: A ball is dropped from rest from the top of a cliff that is 24 m high. From ground level, a second ball is thrown straight upward at the same instant that the first ball is dropped. The initial speed of teh second ball is exactly the same as that with which the first ball...
  23. K

    Relative Velocity Rain Fall Problem

    Hi, Can someone please check my work and tell me where I am going wrong? Rain is falling vertically downward with a velocity 25m/s. A cyclist is moving from North to South vith a velocity 15m/s. What is the velocity of the rain with respect to the cyclist? What is the direction the cyclist has...
  24. zoobyshoe

    An Account of the Fall Of a Meteoric Stone

    "An Account of the Fall Of a Meteoric Stone..." This is a very interesting series of letters followed by a chemical analysis, concerning a meteor that exploded over South Africa in the 1830's. I happened to find it when searching for articles by M. Faraday in the archives of the Royal...
  25. D

    Head Fall Acceleration Question

    Hello, I'm not particularly looking for the answers in this problem as much as I am looking for the method to the solution. It's been giving me a headache. 1. Traumatic brain injury such as concussion results when the head undergoes a very large acceleration. Generally, an acceleration...
  26. K

    Free Fall (kinematics-what I do wrong?)

    A rock is tossed straight up with a velocity of +20m When it returns, it falls into a hole 10m deep. What is the rock's velocity as it hits the bottom of the hole? So basically it is asking for the impact speed right? So that would be Vf^2=Vi^2 +2adelta(s) Vf^2=0+2*9.8*30.41 Vf^2=24.41 It...
  27. B

    Free Fall Scenario: 100kg Piston Kinetic Energy After 20m Drop

    Lets say you have a piston falling in a long cylinder. The piston weighs 100kg but only weighs 1kg under water. The cylinder is filled with water, but there is plumbing going from the bottom of the cylinder to the top. As the piston falls the water can move in a continuous loop, from the bottom...
  28. C

    Free Fall or What? Weight Change Explained

    free fall or what??!? I would like to know, if we are on a lift going upwards, and we happen to be standing on a weighing machine, why does our the value appears more than when we just weigh in the stationary lift??
  29. Lisa!

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  30. I

    Vertical fall with quadratic air drag.

    Hello all, I've been having some problems regarding the fall of an object in the vertical direction that has air drag which varies quadratically with speed. The problem is as shown: A gun is fired straight up. Assuming that the air drag on the bullet varies quadratically with speed. Show...
  31. wolram

    Honoring the Best Fall Guy: Cyrus vs. Penguin

    We should have an award for the best fall guy, for me it would be a hard choise between Cyrus and penquin. :smile:
  32. S

    Why Doesn't the Moon Fall When Orbiting Earth?

    This is a basic question I always had trouble understanding. As moon is orbiting earth, is it coming close? Now it might be for other factors but my point is, Earth has some gravity force on it so even if something is orbiting earth, it should be coming to close to it unless it is fast enough...
  33. M

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  34. F

    Are there any other UCLA Fall 2006 transfer students?

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  35. marcus

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  36. O

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    Whenever I see footage of divers, free falling off a cliff into an deep ocean inlet, I empathize the sensation of danger they are facing. This prompted a question in my mind, that applies to both physics and biology. If the water is plenty deep and there are no obstructions between the cliff...
  37. L

    What tech electives do you think I should take this fall?

    Hello, I am having some difficulty choosing a course to take for this fall. The course is to fill in my technical elective. I am already filling in my other tech electives with an advanced electronics class (with lab), advanced digital (with lab), and opto electronics (with lab). Now, I just...
  38. W

    How do satellites stay in orbit? Free fall or centripetal?

    Hi, I just recently posted this on the astrophysics forum but thought it would probably not quite fit so i decided to move it here. Hi, this is my first post. I have been trying to find an answer out of my own interest but is unable to do so. while searching I found this wonderful website. I...
  39. P

    Compare acceleration to free fall acceleration

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  40. G

    Will the barometer reading rise or fall ?

    If i have a barometer which reads 76cm of hg when kept in an elevator when the elevator is at rest . now the elevator starts going up with some acceleration . will the barometer read less than , greater than or equal to 76cm of hg . also explain why . what will happen if the barometer is under...
  41. P

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    On planet Tehar, the free fall acceleration is the same as that of Earth, but there is also a strong downward electric field that is uniform close to the planet's surface. A 4.05 kg ball having a charge of 4.65 \mu C is thrown upward at a speed of 22.2 m/s, and it hits the ground after an...
  42. E

    Why electron doesn't fall into nucleon in a atom?

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  43. M

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  44. recon

    Calc Fall of Object from Space: Derive Eqn of Accel as Fxn of Time

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  45. J

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  46. P

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  47. L

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  48. C

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  49. S

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  50. K

    Calculate Distance of Roof Above Window Top

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