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. N

    Free fall detect of rotating object

    Hello I have a projectile project. we throw an object with variable speed but about 80 mps and about 90 degrees from Earth level. our goal is to find maximum height that is usually between 250 to 350 meters by means of 3 axis accelerometer and 3axis gyro ( MEMS technology ). In fact we use...
  2. D

    What's the equivalent distance of fall for 1500G

    Hi friendly physics gurus. I'm trying to find equations to help answer a question I have inside my own head. I know the weight of an object (w=170g). I know the object will be subject to a shock of (1500G and time to stop t=0.5ms). My question is: what's that like in terms of how high in the...
  3. S

    Linear Motion and Free Fall: Solving Projectile Motion Problems

    I. Free Fall Motion A mass m = 544 g is thrown straight up with an initial speed of 3.50 m/s from a height of h = 2.50 m Neglecting a drag force, determine: 1. The acceleration of the object while it moves up. 2. The acceleration of the object at the highest point. 3. The maximum height...
  4. A

    Short Webpage Title: Ball Toss Free Fall Equations

    Homework Statement Two students are on a balcony a distance h above the S street. One student throws a ball vertically downward at a speed vi ; at the same time, the other student throws a ball vertically upward at the same speed. Answer the following symbolically in terms of vi, g, h, and t...
  5. A

    How Fast Was the Second Stone Thrown to Match the First at the Cliff Base?

    Homework Statement a stone is dropped from a cliff 200m high.if a second stone is thrown verticall upwards 1.50seconds after the first was released.strike the cliff base at the same instant as the first stone.with what velocity was the second stone thrown 2. Homework Equations Xf=xi +vt +...
  6. A

    What Determines the Meeting Point of Two Falling Stones?

    Homework Statement A stone is dropped from rest from the roof of a 100-m high building; 2.00 s after that, a second stone is thrown straight down with initial speed v0, and the second stone passes the first stone 21.6 m above ground. (a) When are the stones at the same height? (b) What was the...
  7. A

    Height of tower given objects dropped from top at same time?

    Homework Statement A stone is thrown vertically upward from the top of the tower with a velocity of 15m/s. Two seconds later a second stone is dropped from the top of the tower.if both the stone strike the ground simultaneously find the height of the towerV1i=15m/s V2i=0m/s t=2s h=? Homework...
  8. A

    Are two objects in free fall hitting the water at the same time?

    Homework Statement An inquisitive physics student and mountain climber climbs a 50.0m high cliff that overhangs a calm pool of water. He throws two stones vertically downward, 1.00 s apart, and observes that they cause a single splash. The first stone has an initial speed of 2.00 m/s. (a) How...
  9. O

    Do all forms of energy fall under 'kinetic' and 'potential'?

    I know that energy is recognized through motion. Even in the mass-energy equivalence a velocity is present even though it is a rest-energy (Not really sure if this would count as a potential energy since there is no 'field' of acceleration that the mass is in) So does kinetic and potential...
  10. P

    Why does a hammer fall the way it was held when dropped?

    I already know that a hammer will drop to the ground on Earth the way it was held, but I don't understand why.
  11. G

    Free fall with + and - Vinitial

    Two objects thrown from a cliff. One with + vinitial (upward) One with - vinitial (downward). Does the one with + vinitial not reach a greater height and thus have a larger vf upon hitting the ground since it falls farther and therefore is subject to gravity longer?
  12. R

    What are the key factors to consider when using springs for cushioning a fall?

    Lets say there is a rigid metal box. It is 1meter wide, 2meters long and an undetermined height. The thickness of the box's metal walls are also undetermined. The entire box weighs 2 metric tons. There is a person lying face down or face up in this box, and inside the box, the bottom and top of...
  13. N

    Simulating Free Fall Using Euler's Method in C

    Homework Statement Write a C program to simulate a falling object. The program should ask for the initial height of the object, in feet. The output of the program should be the time for the object to fall to the ground, and the impact velocity, in ft/s and miles/hour. Your program should use...
  14. K

    MHB Intial Velocity of an Object In Free Fall

    So I have to calculate the initial velocity of an object I dropped from 2.195 meters that took .96 seconds to hit the ground, given that the Earth's gravitational pull is 9.81m/s^2. What direction/step should I first take in order to solve this? I'm not asking for the answer just a step or two...
  15. A

    Why won't objects fall out of orbit

    I kind of understand how orbit works. So an object falls 10 feet then the Earth's curve counteracts the 10 feet, so it's prevents the object from just crashing down to earth. But wouldn't the object slowly either come closer to Earth or go away from earth. As in like millimeter by milimeter.
  16. Frankenstein19

    Help with free fall and Newtons second law problem

    Homework Statement Using Newtons second law, if an object with mass M is free falling (the only F acting upon it is its own weight), calculate the object's acceleration. What would happen to its acceleration should its mass duplicate? Homework Equations F=ma The Attempt at a Solution So...
  17. B

    Calculate Free Fall Time for 10.0m w/ g=1/6 Earth's g

    Homework Statement Calculate the length of time it would take for an object to fall 10.0m if g were one sixth the value of Earth's g. g=1/6(-9.8)= -1.633333333 m/s^2 a=-1.633333333m/s^2 displacement=10.0m[down] Homework Equations Maybe one of the big 5 kinematics equations? Or maybe...
  18. G

    Why is gravitational acceleration independent of test masses?

    how two objects hit the ground at same time regardless of their weight of masses. what is the reason of Acceleration is always constant via gravitational force for both of them. F=mg F1/m1=F2/m2
  19. D

    Descend Speed After Dropping Glasses: 9.8 m/s

    Homework Statement While parachuting, you dropped your sun glasses at a height of 1400m and it took 15 seconds for the glasses to fall onto the ground. What is your descend speed after you dropped your sun glasses? Homework Equations Y = VoT + 1/2at^2 The Attempt at a Solution My thought...
  20. B

    Calculating Final Velocity in Free Fall from Given Displacement and Acceleration

    Homework Statement The Drop Zone drops riders 27m from rest before slowingthem to a stop. How fast are they moving before they start slowing down? vf=? vi=0, di=27m[up], df=om, displacement=27m[down], acceleration=9.8m/s^2[down] Air resistance is negligable Homework Equations...
  21. RJLiberator

    Free fall velocity with air resistance/drag

    Homework Statement I am analyzing free fall motion in my computer code class. We haven't really discussed much about air resistance and it is a bit of a foreign topic for me. I am searching the internet as much as I can for information on it, but would really appreciate talking to someone here...
  22. RJLiberator

    Comp Sci C++ Free Fall Velocity Homework

    Homework Statement I'm using ROOT (c++) to graph a numerical representation of the equation of motion. For simplicity, I am using initial velocity = 10 and initial height = 10. change in time = 0.05 so we find velocity by V_n = V_(n-1) -9.81*0.05 For some reason, this code is not giving me a...
  23. RJLiberator

    Understanding the Free Fall Velocity Equation

    Homework Statement I am tasked with coding some graphs regarding free fall motion. I am unclear what the professor means regarding the following, so I am looking for incite here. Problem: Solve numerically free fall velocity equation (problem 1.1), compare with exact solution (1.1) dv/dt =...
  24. P

    Calculating Time of Fall: Elevator Problem

    Homework Statement An elevator is ascending with a uniform velocity 2 m/s when a loose bolt gets detached from the ceiling and falls on the floor. If the ceiling is 3 m above the floor , find the time required by the bolt to fall from the ceiling to the floor? (g=10 m/s2) Homework EquationsThe...
  25. G

    Fall 2016 Schedule: Preparing to Transfer for Fall 2017

    I know it's really early in the year, but I want to have some opinion of my POTENTIAL fall 2016 schedule. No harsh comments.Taking calc 1 over the summer. I've been preparing since of December as I've been practicing my algebra skills. I'm taking Precalc this semester! There will be two...
  26. N

    Penn State PHD -- What am I expected to know before Fall semester?

    My question is directed at anyone who currently is enrolled or was enrolled in Penn States PHD program as well as any faculty. Any other advise though would of course be appreciated. I was wondering what am I expected to be proficient in or to know prior to me starting in the fall semester...
  27. G

    Is My Calculation for Free Fall Acceleration Using a Single Photogate Accurate?

    Homework Statement Can free fall acceleration be determined by dropping a marble through a single photogate? The CPO timer attached to the photogate can measure the time it takes for the marble to pass between the arms. Knowing the diameter of the marble enables one to calculate the speed. If...
  28. J

    Is it possible for a person in motion to fall over a ledge?

    The facts are that the person is 183cm, 82kg, meaning his center of gravity is about at 105cm, he was running towards a railing of a balcony that is 108cm high, and allegedly hit the railing then fell over. Is this physically possible?
  29. Creaver

    James Jumps: Calculating the Fall in Seconds & Meters

    Homework Statement To escape the fire which has just declared itself in the building, James jumps through the window. One second before reaching the mattress, he traveled half of the height of fall. What is the total time of the fall in seconds ? What is the total height of the fall in meters...
  30. A

    Do I need to fall in love of everything?

    I'm a second year grad student within engineering physics and after this I am going to take a master in theoretical physics. My plan is to go even further with a PhD when I am done. The thing is, I really don't enjoy some parts of my education. I love the theoretical part of almost everything...
  31. dwinsemius

    Coin rolling on another coin, when will free fall occur?

    Homework Statement Doing this from a memory of a final exam question from freshman physics that I could not solve 45+ years ago. A coin of radius R is poised at the top of another (fixed) coin of radius 2R. If it rolls with no slip, at what point will the top coin leave the lower coin. (I...
  32. Bryson Stevens

    What is the spring constant for the bungee cord used in the given scenario?

    Homework Statement A 84.0-kg bungee jumper steps off a bridge with a light bungee cord tied to her and to the bridge. The unstretched length of the cord is 15.0 m. The jumper reaches reaches the bottom of her motion 38.0 m below the bridge before bouncing back. We wish to find the time interval...
  33. T

    Probability a sample mean will fall in a range

    Homework Statement A random sample of size n = 81 is taken from an infinite population with the mean μ = 128 and the standard deviation σ = 6.3. With what probability can we assert that the value we obtain for the sample mean X will fall between 126.6 and 129.4?The Attempt at a Solution z =...
  34. N

    How can you land safely when falling from free fall?

    Hi I'm trying to explain how this cartoon is physically impossible I know its impossible from common sense, but i don't know how to explain it using physics terms So my questions are: 1) Does the air resistance force have to be much greater than the Fgrav to make you land safetly? If so...
  35. ptownbro

    Electron Energy Level Fall at a Given Wave Length

    1. Homework Statement An electron in the H atom falls from n=(?) to n=3. The wave length of the emitted photon is 1100 nm. From what level did the photon fall? Homework Equations Used the following to get the Energy. w = c / v E = h * v E = h * (c/w) w = lambda (couldn’t figure out how to...
  36. I

    A rod in free fall with varying length

    Suppose you have a weightless rod with at the endpoints two masses. This is a special rod whose length varies in time as a function L(t). If I consider this rod in free fall my intuition is that this rod will rotate for suitable L(t). However, I want to write down the equations of motions for...
  37. Alettix

    Velocity when falling into planet

    Homework Statement Hi! I would need a little help with the following problem: We have found a new planet with density ρ and radius R, and drill a hole to its center. Then accidentally, one person falls into the hole. What is his velocity when reaching the bottom (the center of the planet)...
  38. E

    How Long Does It Take a Dropped Bag to Fall from a Helicopter?

    1. The problem statement, all variables andi given/known data A helicopter ascending at a velocity of 5.0m/s drops a bag at 105 m. How long does it take the bag to fall?Homework Equations X=vit+.5at^2 The Attempt at a Solution I've tried the equation above but i can't solve for time
  39. Adrian F

    Falling Through a Hole in the Earth: GR Effects on Motion

    Hi, folks. There's a somewhat popular hypothetical situation that involves a person falling into a hole dugg all the way through the Earth or any planet, passing straight to its center. Now, I understand quite well that the resulting motion would be periodical and the reasoning behind it. My...
  40. UMath1

    Exploring Torque and Angular Acceleration in Nonuniform Free Fall

    I am confused about whether objects when a nonuniform mass density experience net torque during free fall. If you take a rod that is heavier on one end and lighter on the other, should it not experience a net torque and angularly accelerate? But at the same time, the acceleration by gravity is...
  41. astrocytosis

    Finding the height of a fall given force on impact

    Homework Statement This is the second part of a two part question. The first part asked for the maximum force that can be applied to a bone with minimum cross-sectional area is 3.0cm2, Young's modulus 1.4 × 1010 N/m2, and can withstand a 1.0% change in length before fracturing. I calculated it...
  42. I

    What Angle Below the Horizontal Does a Hockey Puck Hit the Ground?

    Homework Statement A hockey puck slides off the edge of a table with an initial velocity of 20 m/s. The height of the table above the ground is 2 m. At what angle below the horizontal does the puck hit the ground? Homework Equations d=Vi(t)+(1/2)at^2 a^2+b^2=c^2 The Attempt at a Solution...
  43. J

    Gravity in free fall equations

    Why is gravity negative in certain equations, such as y = yi + vi t + (1/2) ( − g ) t^ 2 , but positive in others like vf^2 =vi^2 +2gh ?
  44. B

    Rope hanging from a table, find time taken to fall off table

    Homework Statement A rope of uniform mass per unit length ##\lambda## and length ##L## lies curled on a table, with a short length ##\delta l## of it hanging through a hole in the table. At time zero, the rope begins to slide through the hole. At what time ##t_c## (in seconds) does the end of...
  45. Lana Elcic

    What is the displacement and velocity of a falling object after 1.0 s?

    Homework Statement A rock is thrown straight down with an initial velocity of 10.5 m/s from the Verrazano Narrows Bridge in New York City. The roadway of this bridge is 70 m above water. Take upwards to be the positive direction. Calculate the displacement and velocity at a time of 1.0 s. The...
  46. Lagraaaange

    Schedule for Senior Fall semester? Advice?

    Taking: 1.Thermal Physics 2. Modern Physics 3. Advanced Lab now the big question 4. Computational Physics/PDEs/or independent studies (research)?
  47. Greg Bernhardt

    Post your 2015 fall class schedule

    Summer vacation is quickly wrapping up :nb) Time to post your 2015 fall class schedule and share with us what you're taking. Also post when your first day back is :smile:
  48. 95Tesla

    Is my Fall Schedule too Difficult?

    I'll be starting my junior year this coming fall, and I want to know what people think about my intended schedule. Quantum Mechanics I (3 cr.) Intermediate Electricity and Magnetism (3 cr.) Wave Motion and Optics Lab with Writing (4 cr.) Numerical Mathematical Analysis (3 cr.) Exploration...
  49. I

    Gravitational Field and free fall

    The acceleration of free fall at the equator is not equal to the acceleration of free fall at the poles.explain?
  50. H

    What is the stupidest fall out/argument you have had

    remember saying my mate looked like a teacher and he didnt speak to me for the rest of the day.
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