- published: 28 Jan 2013
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A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid (such as air or water) is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's principle and Newton's third law. A propeller is often colloquially known as a screw.
The principle employed in using a screw propeller is used in sculling. It is part of the skill of propelling a Venetian gondola but was used in a less refined way in other parts of Europe and probably elsewhere. For example, propelling a canoe with a single paddle using a "j-stroke" involves a related but not identical technique. In China, sculling, called "lu", was also used by the 3rd century AD.
In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the water at the effective angle. The innovation introduced with the screw propeller was the extension of that arc through more than 360° by attaching the blade to a rotating shaft. Propellers can have a single blade, but in practice there are nearly always more than one so as to balance the forces involved.
Kyle Andrew Walker (born 28 May 1990) is an English footballer who plays as a defender for English Premier League club Tottenham Hotspur, and the England national football team.
Walker was born in Sheffield and grew up in the Sharrow district of the city. He attended Porter Croft Infant & Junior School, followed by High Storrs School until 2006.
Walker joined boyhood club Sheffield United at the age of seven after being recommended by Football Unites, Racism Divides and progressed through the ranks to become a regular fixture in the reserves by 2008.
In November 2008 he was allowed to join League One side Northampton Town for a month's loan to gain first team experience, making his debut on 15 November 2008 in a defeat at the hands of Oldham Athletic. His one month loan was later extended into January, before eventually returned to Bramall Lane having played nine games for the Cobblers.
Soon after returning to his parent club, Walker made his full debut for Sheffield United on 13 January 2009 starting in a third round FA Cup tie against Leyton Orient. With the Blades losing a number of players to injury in the closing weeks of the season, Walker was a surprise inclusion in the starting line up for the crucial last two games of the season. He made his full league debut for the club on 25 April 2009 against Swansea City. After two outstanding performances he retained his place as Sheffield United entered the play offs, starting both games against Preston North End and the final against Burnley at the end of May. By playing in the final, Walker became the youngest Sheffield United player ever to play at Wembley Stadium.
Cut down the mask
Hide it there
I'm tired of thinking
Let them betray you
Behind the scenes
They throw you up and down
And up and down again
You still wonder why
Sit down and cry
Today your whole world will die
You couldn't name it
It's shame
Again, again, again
It's a fact that you are small
I can't be there waiting
Let them betray you
Behind the scenes
They throw you up and down
And up and down again
You still wonder why
Sit down and cry
Today your whole world will die