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Table of contents Introduction……………………………………………………pg .1 Web of Ideas…………………………………………………..pg .2 Abstract ……………………………………………………… pg .3 Body Report …………………………………………………...pg .4 Conclusion……………………………………………………..pg .8 Bibliography…………………………………………...............pg. 9 Introduction A Force is a push or pull that gives energy to an object sometimes causing it to start moving stop, or change direction. Pressure is a force that acts over a certain area. Buoyancy is the phenomenon caused by the upward force of fluid pressure. Forces, which do not act uniformly on all parts of a body, will also cause mechanical stresses. In out project we will try to explain & demonstrate how an egg can be completely sucked into a small bottle & how little amount of force can make something 10 times its weight. WEB OF IDEAS 1 Force is a push or pull Force gives an object to move .stop moving or change direction They are many kinds of forces such as electromagnetic forces. Nuclear forces, elastic forces and friction. Fluid in motion The faster a fluid moves the less pressure it exerts. FORCES Sliding Rolling Fluid The buoyant force on an object in an equal to the weight of the fluid displaced by the objected this relationship in called Archimedes principle FRICTION 2 Abstract A force is a push or a pull. Force gives an object the energy to move, stop moving, or change direction. We will never be able to move without exerting forces on things. Friction is a force that opposes motion. Without friction, an object would continue to move at a constant speed forever. The different forms of friction are sliding, rolling, and fluid. FORCES & MOTION 3 As we mentioned a force is a push or pull. Forces go way back to the 1600´s. 1687 to be exact. That was the year Sir Isaac Newton sought to describe the motion of all objects using the concepts of Inertia and Force. Doing so Newton established three laws of motion that till this very moment are the way forces are described in physics. In brief, Newton’s first law states that objects continue to move in a state of constant velocity unless acted upon by an external net force or resultant force. Newton’s second law asserts the proportionality of acceleration and mass to force. The third law is a result of applying symmetry to situations where forces can be attributed to presence of different objects. There are many types of forces like; normal force, friction, tension, elastic force, electromagnetic forces, gravity, nuclear force, among many others. Forces are often described as pushes or pulls as we mentioned before. They can be due to the phenomena such as gravity, magnetism, or anything else that might cause mass to accelerate. Did you know… that the concept of force was essential to the development of mechanics and all of physics! Yes, it’s true! Imagine without force, gravity wouldn’t exist, and we would all just be floating in the air. To be able to understand better about the relationship with force and gravity we’ll have to define the concept. The natural phenomenon where objects with mass attract each other is called gravitation or gravity. Gravity is responsible for keeping the Earth and other planets in orbit around the sun. It is also responsible for keeping the moon in orbit around the Earth. Have you ever heard the phrase “What goes up, must come down”? Well this phrase is a great example or gravity. Because of gravity, an object that is close to Earth falls toward the surface of the planet. If an object that is already on the surface experiences a downward force due to gravity. This experience is the force on our bodies as our weight. Another force is Electromagnetic force. Electromagnetic force is the force that in, which an electromagnetic field exerts on electrically charged particles. Electromagnetic force is what holds electrons and protons together in atoms, and hold atoms together in order to make molecules. Originally, electricity and magnetism were thought of as two separate forces. The electromagnetic force is one of the four fundamental forces. The other fundamental forces are: the strong nuclear force, the weak nuclear force, and the gravitational force. The electromagnetic force is responsible for basically all of the things a person encounters in daily life, besides from gravity. In other words, all the forces involved in interactions involving atoms can be tied to the electromagnetic force acting on the electrically charged protons and electrons inside the atoms. 4 The nuclear force is the force between two or more nucleons. It is responsible for the attachment of protons and neutrons into the atomic nuclei. Sometimes the nuclear force is called the residual strong force, in contrast to the strong interactions which are now understood to arise from quantum chromo dynamics or (QCD). Since nucleons have no color charge, the nuclear force does not directly involve the force carriers of quantum chromo dynamics, the gluons. Another type of force in physics is Tension. This type of force is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another. It is also the opposite of compression. Since tension is a type of force, it is measured in Newton’s (N). It is always measured parallel to the string on which it applies. There are two main possibilities for systems of objects held by strings. One of them is acceleration is zero and the system is therefore in equilibrium or there is acceleration and otherwise a net force is present. Friction is the force resisting the relative lateral motion of solid surfaces, fluid layers, or material elements in contact. Friction is not one of the fundamental forces, since it is copied or derived from electromagnetic force between charged particles, including electrons, protons, atoms, and molecules, concluding that it cannot be accepted as a first principle. When contacting surfaces move parallel to each other, the friction between the two surfaces converts into heat. Friction, if acting alone, will cause a moving object to slow down and finally stop. There are three types of friction. Rolling, sliding, and fluid friction. When solid objects slide over each other, the type of friction that results is called sliding friction. The friction produced by objects such as wheels or ball bearings is called rolling friction. That is why most of the times wheels are often placed under objects that are being moved. Sliding friction and rolling friction describe friction between two solid surfaces, but friction also exists when an object moves across or through a fluid. This type of friction is described as Fluid friction. Fluid friction occurs when a fluid exerts the force. Friction is a very helpful force. Without friction we wouldn’t be able to walk. When an object is placed in a fluid, the fluid exerts an upward force. This upward force is known as buoyant force. The buoyant force comes from the pressure applied on the object by the fluid. Because the pressure and the depth both increases, the pressure on the bottom of an object will always be larger than the force on the top. No matter whether an object sinks or floats, there is always a buoyant force present. Buoyancy is the upward force, caused by fluid pressure that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least seem lighter. The buoyant force on an object is equal to the weight of the fluid displaced by the object. The relationship that is between buoyancy and weight is called Archimedes´ principle. Depending on the size of the buoyant force, we can determine what will happen to an object placed in a fluid. In other words if the object will sink or stay afloat. 5 When an object floats it is because it displaces a volume of fluid whose weight is greater than or equal to its own weight. Even though, we ask ourselves why do objects even float? The reason is because of the physical property called density. Density is the ratio of the mass of a substance to its volume. So to speak, density is mass divided by volume (D=M/V). Now that we know what density is, the condition for floating can be stated in terms of density. An object will float in a fluid if the density of that object is less than the density of the fluid. Pressure is caused by force. The forces that exist in fluids are caused by the mass and motion of the particles making up the fluid. The “push”, or force, particles exert over a certain area is called pressure. Fluid pressure is exerted equally in all directions. There are many differences in pressure. Fluids will often move from areas of higher pressure to areas of lower pressure. The transmission of pressure equally in all directions in a liquid is the principle behind hydraulic devices. Hydraulic devices produce enormous forces with application of only a very small force. Conclusion 6 Before reading on this subject we didn’t knew how great of importance it is to have forces. In this project we discovered that there are many types of forces, without this forces we wouldn’t be able to do everyday things like walking, or even being alive 7 Bibliography http://en.wikipedia.org/wiki/Force http://www-istp.gsfc.nasa.gov/stargaze/Snewton.htm http://www.sambal.co.uk/forces.html http://hyperphysics.phy-astr.gsu.edu/hbase/HFrame.html http://dictionary.reference.com/browse/force+ http://thesaurus.reference.com/ http://physics.bu.edu/~duffy/semester1/c23_buoyant.htmlphysics Exploring Physical Science TASKS 8 Clariza: Roberta Porras: Ana Cecilia Cueva: Ana Paulina T: 9