Se muestran los artículos pertenecientes a Mayo de 2017.

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  - Now read a few definitions about the difference between mass and weight. After reading them try to write your own definition with your own words about the difference between mass and weight :




   Definition 1 :

In common usage, the mass of an object is often referred to as its weight, though these are in fact different concepts and quantities. In scientific contexts, mass refers loosely to the amount of "matter" in an object (though "matter" may be difficult to define), whereas weight refers to the force exerted on an object by gravity.[1] In other words, an object with a mass of 1.0 kilogram will weigh approximately 9.81 newtons on the surface of the Earth (its mass multiplied by the gravitational field strength).

(The newton is a unit of force, while the kilogram is a unit of mass.)

Its weight will be less on Mars (where gravity is weaker), more on Saturn, and negligible in space when far from any significant source of gravity, but it will always have the same mass.

 

    Definition 2 :

   A better scientific definition of mass is its description as being composed of inertia, which is the resistance of an object being accelerated when acted on by an external force. Gravitational "weight" is the force created when a mass is acted upon by a gravitational field and the object is not allowed to free-fall, but is supported or retarded by a mechanical force, such as the surface of a planet. Such a force constitutes weight.[2] This force can be added to by any other kind of force.
 

   Definition 3 :

While the weight of an object varies in proportion to the strength of the gravitational field, its mass is constant (ignoring relativistic effects) as long as no energy or matter is added to the object.[3] Accordingly, for an astronaut on a spacewalk in orbit (a free-fall), no effort is required to hold a communications satellite in front of him; it is "weightless". However, since objects in orbit retain their mass and inertia, an astronaut must exert ten times as much force to accelerate a 10‑ton satellite at the same rate as one with a mass of only 1 ton.

On Earth, a swing seat can demonstrate this relationship between force, mass, and acceleration. If one were to stand behind a large adult sitting stationary on a swing and give him a strong push, the adult would temporarily accelerate to a quite low speed, and then swing only a short distance before beginning to swing in the opposite direction. Applying the same impetus to a small child would produce a much greater speed.



  Definition 4 :





  Definition 5 :







   * Have you really understood the difference ?  then...try to do these exercises :


      Wording  1: 

     You are on the earth and have a bag of apples which weights 85N.  If you were to carry
the bag of apples to the surface of the moon, where the gravitational field is
only 1.67 N/kg, how much would the apples weigh?




       Wording 2 :

      An 80 kg person on
top of Mt. Everest would weigh only 781.6 N. 
How strong is the Earth’s gravitational field on top of Mt. Everest?




        Wording 3 :

       If you went to the
moon, how much would you weigh?




        









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   - Next week, during the watch hours (horas de guardia) you will have to do the following tasks. Pay attention to them because they consist in a very important concept (friction).




  - TASK 1 :  Watch the following videos in order to remember the most important concepts about Newton’s laws we have already studied and after that watch the videos about friction because later you will try to achieve a few exercise with a friction force involved :











   - Video 1 of a friction force excercise.   (Pay attention when watching this video!!)






   - TASK 2 :   * Because this friction force exercises are not the easiest at all, I’m gonna post for you a few videos in spanish in order to get them well understood :








   - TASK 3Read very carefully pages 63, 64 and 65 of your book about friction.
                                Look up and read carefully the examples done there on this pages.






   - TASK 4 :   - Do the exercises  10, 11, 12, 13 and 14  from pages  63, 64 and 65  of your book.










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- Noelia ha fet un molt bon treball amb el programa de GIMP modificant la següent imatge del següent link a l'enllaç número 1 i transformant-la en la que es veu en aquest article i que es pot veure més gran en l'enllaç número 2.      Aquí els tens :














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- Cal que us descarregueu els arxius que us agradin de sons d’animals a la següent web i després que els enganxeu a la foto de l’animal que haveu enganxat en un PowerPoint NO del DRIVE, cal que sigui una presentación Powerpoint, no del PowerPoint del drive perquè el del drive no deixa insertar arxius d'audio mp3.


   *     Per tant el que cal que feu és el següent : 

          Enganxeu fotos d’animals a un PowerPoint, però no el que hi ha al drive, després en aquesta web que us dono descarregueu els corresponents arxius de so amb els sons dels animals que us agradin i els enganxeu a la foto de l’animal del PowerPoint, de tal manera que, al PowerPoint , quan feu click sobre la foto s’escolti el so que fa aquest animal .  
           Aquí teniu l’enllaç per descarregar els sons dels animals en mp3 :




                                                                          SONS D’ANIMALS.






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- Cerca a internet i investiga quins components té un altaveu i quin material o component fa que un altaveu tingui un so potent i de què depèn la potència d’un altaveu potent com el del MEGABOOM.


   * Fes un treball en PowerPoint o Word i penja-lo al teu bloc. Aquí tens algunes pàgines que pots consultar :




 








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  - We are going to learn in this lesseon about a magnitud close related to forces, the pressure into a fluid and the statics into fluids. We will also learn too about atmospheric pressure and other issues.

    We will begin studying how a force acting over a Surface can cause pressure.


    * More links will be added soon :
   


     Pressure 1