Free fall

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In Newtonian physics, free fall is any movement of the body in which gravity is the only force acting on it. In the context of general relativity, where gravity is reduced to the curvature of space-time, the free falling body has no power at work for it.

An object in the technical sense of the term "free fall" may not necessarily fall in the usual sense of the term. An object moving upwards is not usually considered a fall, but if it is subject to the force of gravity alone, it is said to fall freely. Such a month fell free.

In a uniform gravitational field, in the absence of another force, gravity acts on every part of the body equally and this is without weight, a condition that also occurs when the zero gravitational field (such as when away from the body of gravity).

The term "free fall" is often used more loosely than in the narrow sense defined above. Thus, falling through the atmosphere without the parachute deployed, or lifting device, is also commonly referred to as free fall . The aerodynamic pull force in such situations prevents them from producing full weight, and thus "free fall" skydiver after reaching terminal speed produces a sensation of weight supported on the air cushion.

Video Free fall

Histori

In the Western world before the 16th century, it was generally assumed that the rate of fall of the body would be proportional to its weight - that is, a 10 kg object is expected to fall ten times faster than an identical 1 kg object through the same medium. The ancient Greek philosopher Aristotle (384-322 BC) discusses the fallen objects in Physics (Book VII) which is probably the first book on mechanics (see Aristotle physics).

The Italian scientist Galileo Galilei (1564-1642) made the Aristotelian theory a careful experiment and observation. He then combines the results of this experiment with mathematical analysis in an unprecedented way.

According to a possible apocryphal story, in 1589-92 Galileo dropped two unequal mass objects from the Leaning Tower of Pisa. Given the speed at which such a fall will occur, it is doubtful that Galileo can gain much information from this experiment. Most of his observations about the fall of the bodies are really bodies that slide down the ramps. This slows everything down enough to the point where it can measure the time interval with its own water clock and pulse (stopwatch has not been found). This he repeats "a hundred times full" until he has achieved "accuracy such that the deviation between two observations never exceeds one-tenth of a pulse." In 1589-92, Galileo wrote De Motu Antiquiora , an unpublished manuscript of the fallen body movement.

Maps Free fall

Example

Examples of free fall objects include:

• Spacecraft (in space) with exhausted driving power (eg in continuous orbit, or on a suborbital trajectory (ballistic) rises for several minutes, then down).
• The object is dropped at the top of the drop tube.
• Objects are thrown up or someone jumps off the ground at low speed (eg air resistance is negligible compared to weight).

Technically, an object falls freely even as it moves upward or instantly rests at the top of its movement. If gravity is the only effect that acts, then acceleration is always down and has the same magnitude for all bodies, usually denoted ${\ displaystyle g}$ .

Since all objects fall on the same level without any other forces, objects and people will experience impartiality in this situation.

Example object not free fall:

• Fly on an airplane: there are also additional lift styles.
• Standing on the ground: the force of gravity is neutralized by the normal force of the soil.
• Down to Earth using a parachute, which balances the force of gravity with an aerodynamic drag style (and with some parachutes, additional lift).

An example of a parachutist falling down is not considered to fall free from a physical perspective, as he experiences the same drag force as his weight after he reaches the terminal speed (see below). However, the term "free fall freefall" is commonly used to describe the case in everyday conversations, and in parachuting communities. However, it is unclear whether the recent winged sport flies in accordance with the definition of free fall plunge.

Near the Earth's surface, a free falling object in a vacuum will speed up about 9.8 m/s ² , independent of its mass. With the air resistance working on the object that has been dropped, the object will eventually reach the terminal speed, which is about 53 m/s (195 km/h or 122 mph) for the human skydiver. Terminal speed depends on many factors including mass, drag coefficient, and relative surface area and will only be reached if it falls from a sufficient height. A typical skydiver in the spread eagle position will reach terminal speed after about 12 seconds, during which time it will fall about 450 m (1,500 ft).

The free fall was shown on the moon by astronaut David Scott on August 2, 1971. He simultaneously removed the hammer and feather from the same height above the lunar surface. The hammer and feather both fall at the same speed and touch the ground at the same time. This shows Galileo's discovery that, in the absence of air resistance, all objects experience the same acceleration due to gravity. (On the Moon, the acceleration of gravity is much less than on Earth, about 1.6 m/s ² .)

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Free fall in Newtonian mechanics

Uniform gravityless field of gravity

This is a "textbook" case of a vertical movement of an object dropping small distance near the surface of the planet. This is a good approach in the air during gravitational forces on objects far greater than air resistance, or equivalent to velocity objects is much lower than terminal speed (see below).

${\ displaystyle v (t) = v_ {0} -gt \,}$

${\ displaystyle y (t) = v_ {0} t y_ {0} - {\ frac {1} {2}} gt ^ {2}} Â Â$

dimana

${\ displaystyle v_ {0} \,}  ÂÂ$ adalah kecepatan awal (m/s).

${\ displaystyle v (t) \,}  ÂÂ$ adalah kecepatan vertikal terhadap waktu (m/s).

${\ displaystyle y_ {0} \,}  ÂÂ$ adalah ketinggian awal (m).

${\ displaystyle y (t) \,}  ÂÂ$ adalah ketinggian berdasarkan waktu (m).

${\ displaystyle t \,}  ÂÂ$ adalah waktu yang terlewati.

${\ displaystyle g \,}  ÂÂ$ adalah akselerasi karena gravitasi (9,81 m/s ² dekat permukaan bumi).

Bidang gravitasi seragam dengan hambatan udara

Kasus ini, yang berlaku untuk skydivers, penerjun atau badan massa apa pun, ${\ displaystyle m}  ÂÂ$ , dan area cross-sectional, ${\ displaystyle A}  ÂÂ$ , dengan nomor Reynolds jauh di atas angka Reynolds kritis, sehingga hambatan udara sebanding dengan kuadrat kecepatan jatuh,                         v                  {\ displaystyle v}    , memiliki persamaan gerak

${\ displaystyle m {\ frac {dv} {dt}} = mg - {\ frac {1} {2}} \ rho C _ {\ mathrm {D}} Av ^ {2} \ ,,}  ÂÂ$

di mana ${\ displaystyle \ rho}  ÂÂ$ adalah densitas udara dan ${\ displaystyle C _ {\ mathrm {D}}}  ÂÂ$ adalah koefisien hambatan, diasumsikan konstan meskipun secara umum akan bergantung pada bilangan Reynolds.

Dengan asumsi objek jatuh dari istirahat dan tidak ada perubahan dalam densitas udara dengan ketinggian, solusinya adalah:

${\ displaystyle v (t) = v _ {\ infty} \ tanh \ left ({\ frac {gt} {v _ {\ infty}}} \ right),}  ÂÂ$

dimana kecepatan terminal diberikan oleh

${\ displaystyle v _ {\ infty} = {\ sqrt {\ frac {2mg} {\ rho C_ {D} A}}} \ ,.}  ÂÂ$

Kecepatan objek versus waktu dapat diintegrasikan sepanjang waktu untuk menemukan posisi vertikal sebagai fungsi waktu:

${\ displaystyle y = y_ {0} - {\ frac {v _ {\ infty} ^ {2}} {g}} \ ln \ cosh \ left ({\ frac {gt} {v _ {\ infty}}} \ right).}  ÂÂ$

Using the 56 m/s figure for the speed of the human terminal, one finds that after 10 seconds it will fall 348 meters and reach 94% of the terminal speed, and after 12 seconds it will fall 455 meters and will reach 97% terminal speed. However, when air density can not be assumed to be constant, as for objects or skydivers falling from high altitudes, the motion equations become much more difficult to solve analytically and numerical simulations of motion are usually required. The figure shows the forces acting on the meteoroids falling through Earth's upper atmosphere. HALO's leaps, including Joe Kittinger and Felix Baumgartner's record leaps (see below), and Le Grand Saut's plans are also included in this category.

The square law inversion square field

It can be said that two objects in space orbiting each other in the absence of other forces fall freely around each other, eg. that the Moon or artificial satellites "fall around" the Earth, or the planet "falls around" the Sun. Assuming a spherical object means that the equation of motion is governed by Newton's Law of Universal Gravitation, with the solution to the problem of two elliptical orbiting gravity bodies obeying Kepler's planetary laws. The relationship between objects falling close to Earth and orbiting objects is well illustrated by the thought experiment, the Newton cannon.

Movements of two objects that are radialally moving toward each other without an angular momentum can be regarded as elliptical orbital special cases of eccentricity e = 1 (radial elliptic paths). This allows one to calculate free fall time for two point objects on the radial path. The solution of this equation of motion results in time as a separation function:

${\ displaystyle t (y) = {\ sqrt {\ frac {{y_ {0}} ^ {3}} {2} left {{\ sqrt {{\ frac {y} {y_ {0}}} \ left (1 - {\ frac {y} {y_ {0}}} \ right)}} \ arccos {\ sqrt {\ frac {y} {y_ {0}}}} \ right)} Â Â$

Where

t is the time after the start of autumn

y is the distance between the body centers

y ₀ is the initial value y

? = G ( m ₁ m ₂ ) is the standard gravity parameter.

Replace y = 0 we get free fall time.

Mengevaluasi hasil ini:

${\ displaystyle y (t) = y_ {0} \ kiri (x - {\ frac {1} {5}} x ^ {2} - {\ frac {3 } {175}} x ^ {3} - {\ frac {23} {7875}} x ^ {4} - {\ frac {1894} {3931875}} x ^ {5} - {\ frac {3293} { 21896875}} x ^ {6} - {\ frac {2418092} {62077640625}} x ^ {7} - \ cdots \ right) \}  ÂÂ$

Where

${\ displaystyle x = \ kiri [{\ frac {3} {2}} \ kiri ({\ frac {\ pi} {2}} - t {\ sqrt { \ frac {2 \ mu} {{y_ {0}} ^ {3}}}} \ right) \ right] ^ {2/3}}  ÂÂ$

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Penurunan gratis dalam relativitas umum

In general relativity, the free fall object is not subject to force and is an inertial body that travels along geodesy. Far from all the sources of the curvature of space, where spacetime is flat, Newtonian free fall theory agrees with general relativity but instead both disagree. The experimental observation that all objects in autumn freely accelerates at the same rate, as noted by Galileo and then manifested in Newton's theory as the equation of gravity and inertia, and then confirmed to the high accuracy by the modern form of the experimental EÃÆ'¶tvÃÆ'¶s, is the basis of the principle of equality, from which the basic theory of general relativity Einstein originally took off.

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Record fell free parachute jump

In 1914, while performing a demonstration for the US Army, a pioneer parachute named Tiny Broadwick spread the parachute manually, making it the first person to jump free.

According to the Guinness Book of Records, Eugene Andreev (USSR) holds the FAI's official record for the longest freefall parachute after falling to 24,500 meters (80,400ft) from a height of 25,458 meters (83,524 ft) near the town of Saratov, Russia on November 1, 1962. Although later on the jumper will rise higher, Andreev notes are set without the use of drogue parachutes during the leap and therefore remain the longest original free falling record.

During the 1950s, Captain Joseph Kittinger of the United States was assigned to the Aerospace Medical Research Laboratory at Wright-Patterson AFB in Dayton, Ohio. For Project Excelsior (meaning "ever riding", the name given to the project by Colonel John Stapp), as part of his research on altitude bailout, he made a series of three parachute jumps wearing pressurized outfits, from helium balloons to open gondolas.

The first, from 76,400 feet (23,290 m) in November 1959 was a close tragedy when equipment damage caused him to lose consciousness, but the parachute automatically rescued him (he went to a flat round with a rotation speed of 120 rpm; g-force in his extremity was calculated to be over 22 times gravity, set another record). Three weeks later he jumped again from 74,700 feet (22,770 m). For his return, Kittinger was awarded the A. Leo Stevens parachute.

On August 16, 1960 he made the final leap from Excelsior III at 102,800 feet (31,330 m). Supports a small parachute parachute for stabilization, it falls for 4 minutes and 36 seconds reaches a maximum speed of 614 mph (988 km/h) before opening the parachute at 14,000 feet (4,270 m). The pressure for his right glove did not work during the climb, and his right hand swelled to twice its normal size. He made notes for the highest climbing balloon, the highest parachute jump, the longest longest fall (4 minutes), and the fastest speed by humans through the atmosphere.

The jump was made in a "rocking" position, down on his back, not the usual curvature that is familiar to the skydivers, as he wears a 60-pound (27 kg) kit behind him and naturally strikes it. shape it when it is inflated, the right shape to sit in the cockpit of an airplane.

For the leap series, Kittinger is adorned with oak leaf clusters to the Distinguished Flying Cross and was awarded the Harmon Trophy by President Dwight Eisenhower.

In 2012, the Red Bull Stratos mission takes place. On October 14, 2012, Felix Baumgartner broke the previous record set by Kittinger for the highest freefall, the highest manned helium balloon flight, and the fastest free fall; he jumped from 128,100 feet (39,045 m), reaching 833.9 mph (1342 km/h) - Mach 1,24 . Kittinger is a member of mission control and helps design capsules and suits that Baumgartner rises and jumps.

On October 24, 2014, Alan Eustace broke the previous record set by Baumgartner for the highest freefall. He jumped from a height of 135,908 feet (41,425 m).

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Surviving

People who fall at low altitude will reach terminal speed after about 12 seconds, falling about 450 m (1,500 feet) at that time. The person will then maintain this speed without falling faster. Terminal speeds at higher altitudes are larger because the atmosphere is thinner and results in lower air resistance; free fallers from the highlands, including Kittinger, Baumgartner and Eustace are discussed in this article, falling faster at higher altitudes.

The severity of the injury increases with the height of free fall, but also depends on the features of the body and the surface and the way the body impacts to the surface. The chance of survival increases if it lands on a soft surface, like snow.

Overall, the height at which 50% of children die from fall is between four and five stories high above the ground.

JAT stewardess Vesna Vulovi? survived the fall of 10,000 meters (33,000 ft) on 26 January 1972 when he boarded the JAT Flight 367. The plane was dropped by an explosive above SrbskÃÆ'¡ Kamenice in the former Czechoslovakia (now Czech Republic). The stewardess of Serbia suffered a broken skull, three spinal fractures (one completely destroyed), and in a coma for 27 days. In an interview, he commented that, according to the man who found him, "... I was in the center of the plane, I was found with my head bowed and my companion over me, one part of my body with my legs on the plane and my head got out of the plane, the caterer trolleel pinned on my back and kept me on the plane The man who found me, said I was very lucky He was in the German Army as a medic during World War II He knew how to treat me at the crash site. "

In World War II there were reports of military aircraft that survived the crash of a severely damaged aircraft: Sgt. Nicholas Alkemade sailed at an altitude of 18,000 feet (5,500 m) without a parachute and survived as he crashed into pine trees and soft snow. He suffered a leg injury. Staff Sergeant Alan Magee got out of his plane at 22,000 feet (6,700 m) without a parachute and survived when he landed on the glass roof of a train station. Lieutenant Ivan Chisov saved about 23,000 feet (7,000 m). While he has a parachute, his plan is to delay opening it because he is in the midst of aerial combat and worries about being shot when hanging under a parachute. He lost consciousness due to lack of oxygen and crashed into snow-covered slopes while still unconscious. While he suffered severe injuries he could fly again in three months.

It was reported that two of the victims of the Lockerbie bombing survived for a short time after hitting the ground (with the front of the nose plane in freefall mode), but died of their wounds before help arrived.

Juliane Koepcke survived a long freefall resulting from December 24, 1971, LANSA Flight 508 crash (LANSA Lockheed Electra OB-R-941 commercial plane) in the Peruvian rainforest. The plane was struck by lightning during a severe lightning storm and exploded in mid-air, decaying two miles (3.2 km) upward. KÃÆ'¶pcke, who was 17 at the time, fell to earth still bound in his seat. The Peruvian German teenager survived the fall with only a broken neck, a wound in his right arm, and his right eye swelled.

As an example of the non-extreme "free survival" as is often reported in the press, a jumpman from Staffordshire is said to have fallen 6,000 meters without a parachute in Russia and survived. James Boole says that he should be signaled by another skydiver to unlock his parachute, but is two seconds late. Boole, who was filming another skydiver for a television documentary, landed on snow-covered rocks and suffered broken vertebra and ribs. While he is lucky to survive, this is not the case of true freefall survival, as he flies winged suits, greatly reducing vertical speed. This is a field that goes down with deep snow, and he is affected when his parachute begins to spread. Over the years, other skydivers have survived an accident in which the press has reported that no parachutes are open, but they are actually being slowed down by a small area of ​​tangled parachutes. They may still be very fortunate to survive, but the impact on 80 mph (129 km/h) is much worse than 120 mph (193 m/h) that may occur in normal free fall.

Jumper parachute and stuntman Luke Aikins managed to jump without a parachute from about 25,000 feet (7,600m) to a 10,000 square foot (930 m ² ) net in California, USA, on July 30, 2016.

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See also

• The equations for falling bodies
• Gravity reduction aircraft
• No weight
• Terminal speed
• High altitude military jumping
• G-force
• The micro-g environment

src: wisconsinskydivingcenter.com

References

src: www.hl.co.uk

External links

• Not Sudden Freefallfall? A slightly cheek-like look on a free fall that survives without a parachute.
• Free fall accident, fall free math - detailed research on the topic
• Freefall formula calculator
• Passengers who jump without moving
• "Joseph W. Kittinger and the Highest Step in the World". Greg Kennedy. March 17, 2010. Ã, Detailed account of origin and project development EXCELSIOR
• The Way Things Falling an educational website
• H.S. Free fall lessons with interactive flash video and animation.

Source of the article : Wikipedia