Skydiver plans head-first freefall from the edge of space in dizzying

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Skydiver plans head-first freefall from the edge of space in dizzying bid to break Mach 1
He will leap head-first from a weather balloon 25 miles above Earth and plummet at more than 1,000mph with only a parachute for
company. He will face external temperatures of minus 100c while inside his carbon-fiber suit it will be a stifling 65c - almost 150
Fahrenheit. And most amazing of all, Michel Fournier is actually looking forward to it. The daredevil Frenchman, a grey-haired 63-yearold former paratrooper, aims to become the first person to break the sound barrier in free-fall.
As he plunges through the stratosphere at supersonic speed, he also hopes to break three more world records - for the longest sky
dive, the highest parachute jump and the highest altitude achieved by a human in a balloon. Despite the intense cold outside, his
£35,000 suit will heat up inside when it meets air resistance. His crash helmet will have its own air supply and reinforced ear pads to
protect him from the sonic boom as he breaks through the Mach 1 sound barrier. Fournier was one of three candidates selected in the
1980s to take part in a military endurance test to see whether a parachutist could descend from 125,000ft - almost 24 miles. The
project was shelved in 1988 - but he decided to go it alone. He hopes to make the jump over the Great Plains of Saskatchewan in Canada
sometime next month, weather permitting.
"I would be lying if I said I wasn't afraid, but I am also very excited," he said."It really is a leap into the unknown."
After leaping from the balloon, Fournier believes he will break the 760mph sound barrier within 37 seconds. The lack of friction due to
the thinness of the air will mean he can attain a much higher terminal velocity, and his team of scientists estimates he will reach the top
speed of 1,113mph before he is slowed down by greater air resistance. His parachute will not open until six minutes, 25 seconds after
jumping and he will finally reach the Earth after around eight and a half minutes. The record for highest leap was set in 1960 by a U.S.
Air Force test pilot, at just under 20 miles.
By IAN SPARKS - 2007
Read more: http://www.dailymail.co.uk/news/article-474879/Skydiver-plans-head-freefall-edge-space-dizzying-bid-break-Mach-1.html
1/ Vocabulary: Translate the dotted underlined words or expressions in the text
Title: « Un parachutiste veut se jeter la tête la première depuis les portes de l’espace afin de tenter le pari fou de dépasser Mach1 »
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Text :
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Skydiver plans head-first freefall from the edge of space in dizzying bid to break Mach 1
Head-first: La tête la 1ière
The edge of space; Edge = bord => “début” de l’espace
Dizzying bid = « tentative vertigineuse »
Leap Head-first = se jeter la tête la première
Plummet at more than 1,000mph = tomber à pic à plus de 1000mph
Carbon-fiber suit = « Combinaison en fibre de carbone »
Stifling = “Suffocant”
Is actually looking forward to it = “est en réalité impatient de le faire”
Daredevil = “Casse-cou”
Old former paratrooper = “ancien parachutiste”
His £35,000 suit will heat up inside = “Sa combinaison à 35000 livres va s’échauffer”
Crash helmet = “Son casque”
Shelved = “Suspendu”
The thinness of the air = “La faible densité de l’air” – Thin = mince
2/ Questions
a/ What is “Mach 1” ?
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Mach number is the speed of an object moving through air, or any fluid substance, divided by the speed of sound as it is in
that substance
b/ “25 miles above Earth”: Could you convert this height into SI units? To answer the question, you can use the eight of Mount
Everest
Data: altitude of Mount Everest in meters = 8848m; its value in ft is given on the document; 1 mile = 5,280 ft.
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Everest ≈ 8848m ≈ 29078ft then, 1ft = (8848/29078) m and 1 mile = 5280 x (8848/29078) ≈ 1607m
25 miles above the Earth = 4.0x104 m = 40 km above the Earth
c/ Convert 1,000mph into km/h and m/s. Give the mathematical relation between the velocity in km/h and m/s
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1 mile = 1609 meters => 1000mph = 1609 km/h
V[km/h] = V[m/s] x 3.6 => V = 1609/3.6 = 447 m/s !!
d/ He will face external temperatures of minus 100c: What are the units used for temperature you know? Is there a lower limit
for the temperature? Why? Same question for an upper limit…
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The temperature depends on the speed of the particles (atoms or molecules).
We have the minimum temperature when molecular kinetic energy is minimal at absolute zero.
Absolute zero is defined as 0K on the Kelvin scale and as −273.15°C on the Celsius scale. Scientists have achieved
temperatures very close to absolute zero where matter exhibits quantum effects such as superconductivity and super fluidity.
We could think there is an upper limit because K = ½ m v² and v is necessarily lower than c = 3x10 8 m/s… But in reality, the
equation, ½ m v²is only right when v << c… When particles move at a speed close to the speed of light, the kinetic energy
becomes infinite. This is why there is no upper limit for the temperature.
Celsius/Fahrenheit:
[°C] = ([°F] − 32) · 5/9
[°F] = [°C] · 9/5 + 32
Celsius/Kelvin: [K] = [°C] - 273.15
e/ What is the sound barrier? Give its value…
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In aerodynamics, the sound barrier usually refers to the point at which an aircraft moves from transonic to supersonic speed.
The air flow around the aircraft reaches the speed of sound. It’s also the case for a whip.
In dry air at 20 °C (68 °F), the speed of sound is 343 meters per second (1,125 ft/s). This equates to 1,236 kilometers per
hour (768 mph).
f/ Why has he used a balloon: why not an airplane?
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Because there is not enough pressure for a plane!
g/ “760mph sound barrier within 37 seconds”: what was its average acceleration in SI units?
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a = change in velocity/change in time
Velocity = 760x1.609 = 1223 km/h = 1223 / 3.6 = 340 m/s
a = (340-0)/37 = 9.2 m/s² = 0.94 g (for a free fall, a = 9.81m/s²)
h/ Is there a terminal velocity for a free fall ? Why? Why did he choose to leap head first from the edge of space?
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Newton’s first law: “In the absence of a net force, the center of mass of a body either is at rest or moves at a constant
velocity”.
During the first part of the fall, air friction is negligible (due to the low pressure): the weight is not balanced and the speed
increases. During the second part, speed and pressure are higher: the friction force is increasing and will balance the weight.
The velocity will be constant.
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