2.  http://www.yout ube.com/watch? v=y0SnFCs9z1g http://www.yout ube.com/watch? v=y0SnFCs9z1g

5.  The question of why some objects sink in fluids while others float can be answered using the law of buoyancy.  This law is known as Archimedes' principle, after the ancient Greek scientist who discovered it.

6. http://www.y outube.com/ watch?v=ijj5 8xD5fDI

7. Archimedes Principle  It can be expressed as ‘Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.  According to a tale, Archimedes discovered this law while taking a bath. After making this discovery, he is said to have leapt out of his bathtub and ran through the streets of Syracuse naked shouting "Eureka!".

9.  If the weight of the water displaced is less than the weight of the object, the object will sink  An object will float, with the weight of the water displaced equal to the weight of the object.

11.  It states that "any body partially or completely submerged in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the body.  " The weight of an object acts downward, and the buoyant force provided by the displaced fluid acts upward. If these two forces are equal, the object floats.

12.  If you’ve ever tried to push a beach ball underwater, you’ve felt this principle in action.  As you push the ball down, it pushes back up. In fact, a big beach ball can be tough to hold underwater. As a physicist in a bathing suit, you may wonder, “What’s happening here?”

13. UNDERSTANDING QUESTIONS  1. Who discover the principle of buoyancy?  2. How did he come up with the conclusion?  3. Explain the principle and use 3 examples, with graphics.  4. What´s the opposite force to gravity (acts upward)?  5. Is it the same if you talk about a ship with cargo or empty? Yes /no? why?  6. g______, b_____ and density work together to determine what floats your boat, or sinks your ship