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Practice 6  A WELL-OILED MACHINE

                               Academic and educational environment
               SOCIAL LANGUAGE PRACTICE:   Paraphrase information to explain the operation
                                        mechanism of a machine.
                                                   Article from Nasa 's
                                                   webpage



            HOW DOES IT WORK?
                                                                aircraft (n.):
                                                                aeronave
            What Is a Helicopter?                              planeador
                                                               glider (n.):

            A helicopter is a type of aircraft that uses rotating or
            spinning wings called blades to fly. Unlike an airplane
            or glider, a helicopter has wings that move.

            Unlike a balloon, a helicopter is heavier than air and uses an
            engine to fly. A helicopter's rotating blades, or rotor, allow it
            to do things an airplane cannot.


            How Does A Helicopter Work?                lift (n.):
                                                       empuje

            In order to fly, an object must
            have "lift", a force moving it
            upward. Lift is usually made by
            wings. Wings create lift because
            of a relationship called the
            Bernoulli Principle.

            The Bernoulli Principle
            describes how the speed of air
            and the pressure in the air are
            related. When the speed goes
            up, the pressure goes down and the opposite is also true.

            Wings are curved on top and flatter on the bottom. This
            shape is called an airfoil. That shape makes air flow over the
            top faster than under the bottom.

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