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. K

    Calculating the Magnitude of an Object in Free Fall

    Heres the question: an 32.8 Newton object is in free fall.what is the mangniutude of the object if it encounters air resistance of 16.6 Newtons? I think you subtract cause air resistance cuts down force: 32.8 - 16.6 = 16.2 Newtons So am i right or do i need to use another equation?
  2. K

    How Does Free Fall Affect Pepe and Babette's Midair Catch?

    Pepe, the clown, is jumping on a trampoline as Babette, the tightrope walker, above him suddenly loses her balance and falls off the tightrope straight toward Pepe. Pepe has just started upward at 15.0 m/s when Babette begins to fall. Pepe catches her in midair after 10.0s. a) How far has...
  3. F

    Where Does the First Second of the Universe Fall on the Time Line?

    I draw a straight line representing the time line of the universe. On this line I put a mark at 1cm and I say this represents the end of the Planck Epoch. So I can understand how tiny the Plank Epoch was, could someone tell me, how far along the line at this scale the first second of the...
  4. P

    Calculating Impulse on Bungee Jumper from 78m Fall

    A bungee jumper (m = 75.00 kg) tied to a 48.00 m cord, leaps off a 78.00 m tall bridge. He falls to 8.00 m above the water before the bungee cord pulls him back up. What size impulse is exerted on the bungee jumper while the cord stretches? I found the velocity by v_final^2= V_inital + 2ad...
  5. D

    Physics Motion and Free Fall Equations

    I am just looking for--or perhaps one of u could just post them--a list of physics motion equations in 1d, and freefall u know v=x/t v(f)=v(i)... v(f)2=v(i)2...etc thx
  6. E

    How Does Air Resistance Affect the Distance of Free Fall?

    Here's the problem: Consider a particle of mass m whose motion starts from rest in a constant gravitational field. If a resisting force proportional to the square of the velocity (kmv2) is encountered, find the distance s the particle falls in accelerating from v0 to v1. I began with the...
  7. Z

    More massive objects will fall faster than lighter objects?

    Was it Aristotle who said that more massive objects will fall faster than lighter objects? This leads me to wonder: why didn't he just experiment with this idea to see that he was wrong? :confused:
  8. A

    Why doesn't the moon fall on earth?

    I am curious as to why the moon doesn't fall into the earth. Did a few searches and found: https://www.physicsforums.com/archive/t-58667_Why_doesnt_the_moon_just_fall_to_the_earth?.html But that doesn't explain one thing. Moons orbit is not an exact circle. Its "almost" circular. So...
  9. P

    Totally Lost (Free Fall Distance)

    Hi, its me...AGAIN! You people should start CHARGING for your services! I have a conceptual problem more than just a homework problem this time. It regards free fall distance and the formula applied. Okey dokey...the formula to find out how far an object falls from rest is: d=1/2 gt^2...
  10. K

    Calculating Velocity in Free Fall from a Given Height

    ok how would i go about solving this an what equations do i use [SFHS99 2.P.40.] A worker drops a wrench from the top of a tower 89.0 m tall. With what velocity does the wrench strike the ground? (Assume the positive direction is upward.) wrong check mark m/s i have to use this...
  11. JamesU

    Body twitches before I fall asleep

    Sometimes, almost every night, when I'm just about to fall asleep, my body shakes orjumps a few inches of the bed. can anyone explain this?
  12. L

    Programs Take a look at my fall schedule (physics/chem dual major)

    Fall semester: Intermediate Inorganic Analytical Chem Analytical chem lab Physical chem 1 physical chem 1 lab Advanced Eng. Math Contemporary Physics Contemp. lab :cry: Spring Semester: Quantum Mechanics Physical chem 2 Physical Chem 2 lab Linear Alg. Advanced Organic...
  13. B

    New GRE in Fall 2006? Check Out Updates at GRE.org

    check this out: http://www.gre.org/grechanges.html so... it might be a good idea to wait until the changes are implemented, if possible, unless you want to be inundated with words that no one will ever know or use! i hope that kaplan is quick with its guides! :-p just givin'...
  14. N

    WTC Metal Fatigue. How Did Building 7 Fall?

    Building 7 was hit by no aircraft or debris. It had several small fires and amazingly collapsed in symmetrical fashion at free fall speeds. We saw in Madrid a building burn at intense levels for MANY hours but not collapse. Is there any scientific explanation for such a catastrophic...
  15. A

    Time taken for a parachute to fall

    Hi. I'm doing a KS3 coursework experiment whereby I need to investigate the question, 'Does the area of a parachute affect the rate of fall?' Obviously the answer is yes, however the theoretical physicist within me wanted to take this much further, so I attempted to pull together my basic...
  16. U

    Will a Ball Take Longer To Rise or Fall?

    if I threw a ball straight up (including air friction), would it take longer for the ball to drop back to its original position from its max height or longer for the ball to rise up to its max height? here's what I'm thinking, on the way up, there is air friction and mg going agaist the...
  17. M

    Schools To those starting grad school this fall: Where have you chosen to study?

    Now that the April 15th deadline has passed, I thought it would be a good idea to find out where all the new graduate students have decided to study. That way, you might be able to find other students going to the same school as you. I chose UC - Santa Barbara. If anybody else is going...
  18. C

    Why Do Objects of Different Mass Fall at the Same Time? Get Answers Here!

    If I drop 2 of the same object but different mass like a pocket book and a encylopedia, they drop at the same time. Why is that? Anyone can get a detailed explanation? Thanks!
  19. S

    The Fall of the Portable Radio: How Long for a 10 dB Increase?

    A portable radio is sitting at the edge of a balcony 5.1m above the ground. The unit is emitting a sound uniformly in all directions. By accident, it falls from rest off the balcony and continues to play all the way down. A gardener is working in a flower bed directly below the falling unit...
  20. L

    Force and Free Fall: 3 Questions Answered

    Can anyone help me with any of these 3 questions? 1. Wrongly called for a foul, any angry basketball player throws the ball straight down to the floor. If the ball bounces straight up and returns to the floor 2.5s after first striking it, what was the ball's greatst height above the floor...
  21. wolram

    The rise and fall of the cosmic string theory

    http://arxiv.org/pdf/astro-ph/0501590 The cosmic string theory for cosmological primordal petturbations has been ruled out.
  22. J

    Projectile explodes at peak where will it fall?

    There is a projectile that explodes into equal mass fragments at its highest point. One falls vertically with initial speed. I need to find where the other will strike the ground and the energy released during the explosion. I am given the mass(19.6kg), angle (56 degress), initial...
  23. A

    Why did China fall behind Europe in technology?

    For much of human history China had a more advanced civilization and technology than Europe. Why did China fall behind Europe in technology? http://www.cba.uni.edu/economics/Gernes.pdf http://www.cronab.demon.co.uk/china.htm
  24. R

    Max Height of Rocket in Free Fall: Solving for a, t1, and g

    I was given the situation, A rocket, initially at rest on the ground, accelerates straight upward from rest with constant net acceleration a , until time t1, when the fuel is exhausted. Find the maximum height H that the rocket reaches (neglecting air resistance). Express the maximum height...
  25. E

    The max. distance of fall of the bungee jumper?

    Please help me to solve this question because I don't have a clue to do that! Q: In a bungee jump a volunteer of mass 70 kg drops from a bridge, tethered to his jump point by an elastic cable of unstretched length L = 20m and elastic modulus 3000 N. Ifnoring energy losses, and assuming he...
  26. cepheid

    Calculating Force of Impact from Unfortunate Fall

    This isn't homework...I was just thinking through this rather morbid scenario and realized that I couldn't remember how to calculate the result I was looking for. The morbid scenario is person falling from a building of height h. How do you calculate the force exerted on the person by the ground...
  27. P

    Why doesnt the moon just fall to the earth?

    I know its in orbit but things like the Hubble telescope need fuel don't they?
  28. U

    What Does the Constant 'b' Represent in the Drag Force Equation?

    free fall with drag force If the equation F=-bv^2 describes the drag force of an object...then the differential equation for the object's motion would be: dv/dt= -g+bv/m or is it... dv/dt= g-bv/m After solving the equation, should I get... V=mg/b[1-e^(-bt/m)] Also, does this...
  29. B

    How Long Does a Cricket Take to Jump Portions of Its Full Leap?

    Heres the question: Some crickets can jump 21 cm, how long does it take the cricket to jump 7cm of that 21cm?
  30. Loren Booda

    Unraveling the Science Behind the Seasonal Changes of Fall

    For those in the Northern Hemisphere (or the Southern Hemisphere, offset by 6 months), why does Fall feel the way it does?
  31. kat

    News Stock on Kerry in an IEM free fall

    Stock on Kerry in an IEM "free fall" Market Quotes: Pres04_WTA.html Quotes current as of 12:31:43 CST, Monday, September 27, 2004. Symbol Bid Ask Last Low High Average DEM04_G52 0.061 0.069 0.067 0.067 0.077 0.072 DEM04_L52 0.210 0.219 0.225 0.207 0.232 0.226 REP04_L52 0.230 0.231...
  32. F

    Free fall (check my solution im stuck) PLEASE HELP ME TODAY

    Q40. A boy stands at the edge of a bridge 20.0 m above a river and throws a stone straight down with a speed of 12.0 m/s. He throws another pebble straight upward with the same speed so that it misses the edge of the bridge on the way back down and falls into the river. For each stone find (a)...
  33. F

    The Acceleration Of Free Fall?

    ''A DART LEAVES THE THROWER HAND HORIZONTALLY AT A height of 1.9m above the ground, calculate the time taken by the dart to reach the board and the horizontal velocity at which the dart left the throwers hand.'' this is what iv worked out x-0.4 u-? v-0 a-0 t-? i than went onto finding...
  34. B

    Solving for Raft Speed in a Free Fall Problem | Bridge, Stone, and River Math

    This class is killing me. Here's my problem: A woman on a bridge 91.0m high sees a raft floating at a constant speed on the river below. She drops a stone from rest in an attempt to hit the raft. The stone is released when the raft has 2.70m more to travel before passing under the bridge. The...
  35. B

    Vector and Free Fall Problem Solving

    Hi again, My first question has to do with vectors again. But it's not hard. I just can't see my mistake. The problem involves two displacement vectors. A which is 3.00km due south, and B which points due east. No value is given for B. However the resultant vector is 4.49km. So of...
  36. C

    Free fall acceleration flowerpot problem

    A flowerpot falls off a windowsill and falls past the window below. You may ignore air resistance. It takes time 0.420 s to pass this window, which is of height 1.90 m. Question- How far is the top of the window below the windowsill from which the flowerpot fell? Take the free fall...
  37. C

    Free Fall Question: Calculate Velocity & Distance

    A student throws a water balloon vertically downward from the top of a building. The balloon leaves the thrower's hand with a speed of 6.35m/s . Air resistance may be ignored, so the water balloon is in free fall after it leaves the thrower's hand. A.) What is its speed after falling for a...
  38. N

    HOw can an egg fall from a high placeto the ground without breaking?

    HOw can an egg fall from a high placeto the ground without breaking?
  39. S

    Free Fall Problem: Calculating Projectile Motion from a Cliff Edge

    Help! Free Fall Problem A pellet gun is fired straight downward from the edge of a cliff that is 13 m above the ground. The pellet strikes the ground with a speed of 30 m/s. How far above the cliff edge would the pellet have gone had the pellet been fired straight upward?
  40. C

    Hot Air Balloon Free Fall Question

    A hot-air balloonist, rising vertically with a constant velocity of magnitude v=5.00m/s , releases a sandbag at an instant when the balloon is a height h=40.0m above the ground . After it is released, the sandbag is in free fall. 1.) Compute the position of the sandbag at a time 0.165s after...
  41. E

    Rocket Free Fall Problem: Calculating Time, Altitude, and Velocity

    Pleeeeeeeeeeeeeeeeease Help! A test rocket is fired vertically upward from a well. Acatapult gives it an initial speed of 79.2 m/s at ground level. Its engines then fire and it accelerates upward at 4.10 m/s^2 until it reaches an altitude of 950m. At that point its engines fail, and the...
  42. W

    Calculating Basketball Player's Hang Time

    A basketball player jumps 1 meter high off the ground, turns around and starts back down. Estimate the time she is within 30 cm of the top of her trajectory (her hang time.) (HINT: Calculate the time it takes to fall 30 cm from rest and double it.) Explain why that works note...
  43. F

    What is everybody taking this fall?

    I've got: Analysis II: Hilbert spaces, Banach spaces, L_p spaces, Lebesgue measure & integration, etc. Textbook is Real Analysis by Royden Algebra III: noncommutative rings, modules, some categories, functors, tensor products, maybe some group representations, etc. Textbook is Algebra by...
  44. E

    Initial Speed of Ball Thrown Horizontally from 15.75m Height

    A ball is thrown horizontally from a height of 15.75 m and hits the ground with a speed that is 5.0 times its initial speed. What was the initial speed? I thought you might have to find time and I got t=1.79s, but after that I cannot seem find my way to the answer Thanks to whom ever can...
  45. P

    How can I solve this free fall problem with missing variables?

    Stumped on free fall problem! This is probably an easy question, but I am stumped!A wrecking ball is hanging at rest from a crane when suddenly the cable breaks. The time it takes for the ball to fall halfway to the ground is 1.2s. Find the time it takes for the ball to fall from rest all the...
  46. S

    Find Velocity for Object to Reach Space & Return in 8 Days

    I am trying to find a velocity for an object that would launch it into space from Earth (straight up, NOT into orbit) and return exactly 8 days later. I cannot use x = v0t + 1/2at^2 (x=0 t=691200 a=9.8 [seconds in 8 days]) because the distance from the Earth changes in such a great way that...
  47. Evo

    City-Sized Asteroid to Pass Earth This Fall

    "On Sept. 29, 2004 an asteroid the size of a small city will make the closest known pass of such a very large space rock anytime this century." "Toutatis looks something like a dumbbell hurtling awkwardly through space. It has a crazy rotation that makes normal days impossible. Scientists...
  48. D

    Calculating the Angle at Which a Marble Falls Off a Smooth Sphere

    a small marble of mass m resting on the top of a smooth sphere of radius R. you nudge the marbles slightly and it starts rolling down the side. at what point (at what angle) on the sphere does the marble fall off the sphere? ans: 48deg ............... after reading my guess is that the...
  49. C

    Solve Physics Free Fall Question: Height of Building

    I'm really bad at physics so please excuse me. But I would like some help on this question. I would like to be able to solve it without plugging in any numbers until the end. If a person steps off a building of height h, and free falls on the way down to the bottom. What is the height of the...
  50. H

    The difference b/t free fall and outer space

    You are in the closed elevator with the apple. You feel weightless. So you want to know whether you're free falling or in the outer space. Place the apple about a meter away from your eyes. If the elevator is in free fall, the apple will move close to you slowly, but if you're in the outer...
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