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Forces and motion

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Forces and motion

1. 1.  A force is a push or pull acting upon an object as a result of its interaction with another object.
2. 2.  Contact Forces-resulted from the contact of two interacting bodies.  Action at a Distance Forces-resulted from the non-contact of two interacting bodies.
3. 3.  Normal Force- The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. On occasions, a normal force is exerted horizontally between two objects that are in contact with each other. For instance, if a person leans against a wall, the wall pushes horizontally on the person.
4. 4.  Tension Force-The tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends. The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.
5. 5.  Spring Force-The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it. An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position. For most springs (specifically, for those that are said to obey "Hooke's Law"), the magnitude of the force is directly proportional to the amount of stretch or compression of the spring.
6. 6.  Frictional Force-The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. There are at least two types of friction force - sliding and static friction. Though it is not always the case, the friction force often opposes the motion of an object. For example, if a book slides across the surface of a desk, then the desk exerts a friction force in the opposite direction of its motion. Friction results from the two surfaces being pressed together closely, causing intermolecular attractive forces between molecules of different surfaces. As such, friction depends upon the nature of the two surfaces and upon the degree to which they are pressed together. The maximum amount of friction force that a surface can exert upon an object can be calculated using the formula below:  Ffrict = µ • Fnorm
7. 7.  Air Resistance Force-The air resistance is a special type of frictional force that acts upon objects as they travel through the air. The force of air resistance is often observed to oppose the motion of an object. This force will frequently be neglected due to its negligible magnitude (and due to the fact that it is mathematically difficult to predict its value). It is most noticeable for objects that travel at high speeds (e.g., a skydiver or a downhill skier) or for objects with large surface areas.
8. 8.  Applied Force-An applied force is a force that is applied to an object by a person or another object. If a person is pushing a desk across the room, then there is an applied force acting upon the object. The applied force is the force exerted on the desk by the person.  Bouyant Force-the upward force exerted by a fluid on a submerged or floating object. The bouyant force is equal to the displaced fluid (Archimedes’ Principle)
9. 9.  Gravitational Force-The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth. The force of gravity on earth is always equal to the weight of the object as found by the equation:  Fgrav = m * g  where g = 9.8 N/kg (on Earth)  and m = mass (in kg)
10. 10.  Magnetic Force-Magnetic force is the attraction or repulsion that arises between electrically charged particles because of their motion. It is the basic force responsible for the action of electric motors and the attraction of magnets for iron.
11. 11.  Electrical Forces-Electrical force is the force that exists between all charged particles. The electric force is responsible for such diverse phenomena as making your hair stand up on a cold dry day, creating chemical bonds, and allowing you to see when you turn on a lamp on a dark night.
12. 12.  The Strong Force This force is responsible for binding of nuclei. It is the dominant one in reactions and decays of most of the fundamental particles. This force is so strong that it binds and stabilize the protons of similar charges within a nucleus. However, it is very short range. No such force will be felt beyond the order of 1 fm (femtometer or 10-15 m). 
13. 13.  The Electromagnetic Force This is the force which exists between all particles which have an electric charge. For example, electrons (negative charge) bind with nucleus of an atom, due to the presence of protons (positive charge). The force is long range, in principle extending over infinite distance. However, the strength can quickly diminishes due to shielding effect. Many everyday experiences such as friction and air resistance are due to this force. This is also the resistant force that we feel, for example, when pressing our palm against a wall. This is originated from the fact that no two atoms can occupy the same space. However, its strength is about 100 times weaker within the range of 1 fm, where the strong force dominates. But because there is no shielding within the nucleus, the force can be cumulative and can compete with the strong force. This competition determines the stability structure of nuclei.
14. 14.  Weak Force This force is responsible for nuclear beta decay and other similar decay processes involving fundamental particles. The range of this force is smaller than 1 fm and is 10-7 weaker than the strong force. Nevertheless, it is important in understanding the behavior of fundamental particles.
15. 15.  The Gravitational Force  This is the force that holds us onto the Earth. It could be important in our daily life, but on the scale of atomic world it is of negligible or no importance at all. Gravitational force is cumulative and extended to infinity. It exists whenever there is matter. Your body is experiencing a gravitaional pull with, say, your computer (or anything close to you or as far away as stars and galaxies) but the effect is so small you will never sense it. However, you can sense the gravitaional pull with the Earth (that is, your weight) due to the cumulative effect of billions of billions of the atoms made up your body with those atoms of the Earth. This means that the larger the body (contain more matter), the stronger the force. But on the scale of individual particles, the force is extremely small, only in the order of 10-38 times that of the strong force.
16. 16.  The gravitational force between two masses is given by:  This formula represents the Universal Law of Gravitation and G is the universal gravitation constant. It means that force is directly proportional to the product of two masses and inversely proportional to the square of the distance between two masses, which is denoted by r. 2 2 11 2 21 1067.6 kg Nm xGwhere r mGm Fgravity   2 2 11 2 21 1067.6 kg Nm xGwhere r mGm Fgravity  
17. 17.  Weight is the force due to gravity. It is the force that pulls the object downwards the center of the earth. The formula for the weight is: 22 328.9 s ft s m gwheremgW earth 
18. 18.  2. Strong Nuclear Force -It is a binding force between two nucleons (neutrons and protons). This is the force that is responsible for holding two nucleons together to form nuclei. The characteristics of strong nuclear force are as follows:  Charge independence-The nuclear force betwen two protons is the same as between two neutrons and between a neutron and a proton.  Saturation-The force needed to tear a neutron from a nucleus is approximately the same regardless of the number of nucleons in the nucleus.  Short range-The force decreases rapidly with increasing distance. At a distance of about 1 femtometer (1 fm-10-15 meter) the strong nuclear forc is attractive (about 10 times the electric force between protons). The force force becomes repulsive when two nucleons are about 0.4 fm from each other. The nuclei do not collapse.
19. 19.  3. Electromagnetic Force It is a force between particles with electric charges. It can either be attractive or repulsive. Its strength is 100 times weaker within the range of 2 fm. This phenomenon has two different characteristics:  Electrostatic force-is the force of two electrically charged particles exerted on one another. This force between two charges is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance separating the charges. This is a law is known as Coulombs Law:  Magnetic force-is the force due to motion of charges. The strength of interaction depends on the separating the two magnets. 2 21 r qkq FE 
20. 20. 4. Weak nuclear force It is the force responsible for beta decay and other decay process involving fundamental processes. It is the interaction between all leptons, which includes electrons, positrons, muons and neutrons and hadrons. Weak force involves the exchange of the immediate vector bosons, the W and the Z. All leptons and hadrons interact via this force.
21. 21.  First Law: Law of Inertia ◦ An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.
22. 22.  Second Law: Law of Acceleration  Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Everyone knows that heavier objects require more force to move the same distance as lighter objects.
23. 23.  Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation:  or FORCE = MASS times ACCELERATION  maF 
24. 24.  This is an example of how Newton's Second Law works:  Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car.  Answer = 50 newtons
25. 25. Momentum-It is also known as mass in motion. It is the product of the mass and the velocity of a body. The formula for momentum is: P=mv Where: m is mass, v is velocity and P is momentum. Impulse –is the change in momentum t P Fnet   
26. 26.  Third Law: Law of Interaction For every action there is an equal and opposite re-action. This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.
27. 27. Example: The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.
28. 28.  Work  refers to an activity involving a force and movement in the directon of the force. A force of 20 newtons pushing an object 5 meters in the direction of the force does 100 joules of work.  Energy  is the capacity for doing work. You must have energy to accomplish work - it is like the "currency" for performing work. To do 100 joules of work, you must expend 100 joules of energy.  Power  is the rate of doing work or the rate of using energy, which are numerically the same. If you do 100 joules of work in one second (using 100 joules of energy), the power is 100 watts. 
29. 29.  Work is the product of the applied force in the direction of motion and the displacement through which the force acts. That is W=Fd If the applied force is not in the direction of the motion, only the part of the displacement parallel to the force’s direction is important. Thus, when the applied force is not in the direction of the motion the work done is cosFdW 
30. 30.  Hooke's Law  The relationship between the force applied to a spring and the amount of stretch was first discovered in 1678 by English scientist Robert Hooke. As Hooke put it: Ut tensio, sic vis. Translated from Latin, this means "As the extension, so the force." In other words, the amount that the spring extends is proportional to the amount of force with which it pulls. If we had completed this study about 350 years ago (and if we knew some Latin), we would be famous! Today this quantitative relationship between force and stretch is referred to as Hooke's law and is often reported in textbooks as Fspring = -k•x  where Fspring is the force exerted upon the spring, x is the amount that the spring stretches relative to its relaxed position, and k is the proportionality constant, often referred to as the spring constant. The spring constant is a positive constant whose value is dependent upon the spring which is being studied.
31. 31.  The work done in compressing or extending the spring by an applied force is  Where x is the distance the spring has been compressed or extended from its equilibrium position. 2 2 1 kxW 
32. 32.  The quantity that has to do with the rate at which a certain amount of work is done is known as the power. The hiker has a greater power rating than the rock climber.Power is the rate at which work is done. It is the work/time ratio. Mathematically, it is computed using the following equation.  Power = Work / time or P = W / t  The standard metric unit of power is the Watt. As is implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time. Thus, a Watt is equivalent to a Joule/second. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine. One horsepower is equivalent to approximately 750 Watts.
33. 33.  Energy, in physics, the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. There are, moreover, heat and work—i.e., energy in the process of transfer from one body to another. After it has been transferred, energy is always designated according to its nature. Hence, heat transferred may become thermal energy, while work done may manifest itself in the form of mechanical energy.
34. 34.  Mechanical Energy is the energy of motion that does the work. An example of mechanical energy is the wind as it turns a windmill.  Heat energy is energy that is pushed into motion by using heat. An example is a fire in your fireplace.  Chemical Energy is energy caused by chemical reactions. A good example of chemical energy is food when it is cooked.  Electrical Energy is when electricity creates motion, light or heat. An example of electrical energy is the electric coils on your stove.  Gravitational Energy is motion that is caused by gravity. An example of gravitational energy is water flowing down a waterfall.
35. 35.  Energy exists in many different forms. Examples of these are: light energy, heat energy, mechanical energy, gravitational energy, electrical energy, sound energy, chemical energy, nuclear or atomic energy and so on. These forms of energy can be transferred and transformed between one another. This is of immense benefit to us. For a source of energy to end up as electricity it may undergo many transformations before it can power the light bulb in your home.
36. 36.  Kinetic energy is the energy in moving objects or mass. Wind energy is an example. The molecules of gas within the air, are moving giving them kinetic energy.  Potential energy is any form of energy that has stored potential that can be put to future use.
37. 37.  For example, water stored in a dam for hydroelectricity generation is a form of potential energy. When valves are opened the force of gravity cause water to begin to flow. The gravitational potential energy of the water is converting to kinetic energy. The flowing water can turn a turbine, which will further convert the kinetic energy of the water into useable mechanical energy. An alternator or generator then converts the mechanical energy from the turbine into electrical energy. This electricity is then sent to the electricity grid and to our homes where it is converted into light energy (lights and televisions), sound energy (televisions, stereos), heat energy (hot water, toasters, ovens), mechanical energy (fans, vacuum cleaners, fridge and air conditioner compressors) and so on.
38. 38.  Gravitational potential energy is energy an object possesses because of its position in a gravitational field. The most common use of gravitational potential energy is for an object near the surface of the Earth where the gravitational acceleration can be assumed to be constant at about 9.8 m/s2. Since the zero of gravitational potential energy can be chosen at any point (like the choice of the zero of a coordinate system), the potential energy at a height h above that point is equal to the work which would be required to lift the object to that height with no net change in kinetic energy. Since the force required to lift it is equal to itsweight, it follows that the gravitational potential energy is equal to its weight times the height to which it is lifted.
39. 39. Thus the formula for the gravitational potential energy is Where PE is the gravitational potential energy, m is the mass of the body, g is the gravitational acceleration and h is the vertical distance, w is the weight of the body. 2 2 1 mvK  whmghPEgravity 
40. 40.  Mechanical energy is the sum of the potential and kinetic energies in a system. The principle of the conservation of mechanical energy states that the total mechanical energy in a system (i.e., the sum of the potential plus kinetic energies) remains constant as long as the only forces acting are conservative forces. We could use a circular definition and say that a conservative force as a force which doesn't change the total mechanical energy
41. 41.  A good way to think of conservative forces is to consider what happens on a round trip. If the kinetic energy is the same after a round trip, the force is a conservative force, or at least is acting as a conservative force. Consider gravity; you throw a ball straight up, and it leaves your hand with a certain amount of kinetic energy. At the top of its path, it has no kinetic energy, but it has a potential energy equal to the kinetic energy it had when it left your hand. When you catch it again it will have the same kinetic energy as it had when it left your hand. All along the path, the sum of the kinetic and potential energy is a constant, and the kinetic energy at the end, when the ball is back at its starting point, is the same as the kinetic energy at the start, so gravity is a conservative force.
42. 42.  A source of energy is that which is capable of providing enough useful energy at a steady rate over a long period of time. A good source of energy should be : i) Safe and convenient to use, e.g., nuclear energy can be used only by highly trained engineers with the help of nuclear power plants. It cannot be used for our household purposed. ii) Easy to transport, e.g., coal, petrol, diesel, LPG etc. Have to be transported from the places of their production to the consumers. iii) Easy to store, e.g., huge storage tanks are required to store petrol, diesel, LPG etc.
43. 43. Characteristics of an ideal or a good fuel: 1. It should have a high calorific or a heat value, so that it can produce maximum energy by low fuel consumption. 2. It should have a proper ignition temperature, so that it can burn easily.] 3. It should not produce harmful gases during combustion. 4. It should be cheap in cost and easily available in plenty for everyone. 5. It should be easily and convenient to handle, store and transport from one place to another. 6. It should not be valuable to any other purpose than as a fuel. 7. It should burn smoothly and should not leave much residue after its combustion.
44. 44. The sources of energy can be classified as follows : (i) Renewable (ii) Non-Renewable. 1. Renewable sources of energy :- Renewable sources of energy are those which are inexhaustible, i.e., which can be replaced as we use them and can be used to produce energy again and again. These are available in an unlimited amount in nature and develop within a relatively short period of time.
45. 45.  Examples of Renewable Sources of Energy. (i) Solar energy, (ii) Wind Energy, (iii) water energy (hydro-energy), (iv) geothermal energy, (v) ocean energy, (vi) biomass energy (firewood, animal dung and biodegradable waste from cities and crop residues constitute biomass).
46. 46.  Advantages of Renewable Sources of Energy : (i) These sources will last as long as the Earth receives light from the sun.  (ii) These sources are freely available in nature.  (iii) These sources do not cause any pollution.
47. 47.  2. Non-renewable sources of energy are those which are exhaustible and cannot be replaced once they have been used. These sources have been accumulated in nature over a very long period of million of years. Examples of Non-renewable sources of Energy : (i) Coal (ii) Oil and (iii) Natural gas. All these fuels are called fossil fuels.
48. 48. (i) Due to their extensive use, these sources are fast depleting. (ii) It is difficult to discover and exploit new deposits of these sources. (iii) These sources are a major cause of environmental pollution.
49. 49.  Sources of energy are also classified as :  (i) Conventional sources of energy  (ii) Nonconventional sources of energy.  Conventional sources of energy : Are those which are used extensively and a meet a marked portion of our energy requirement and these are : (a) Fossil fuels (coal, oil and natural gas) and (b) Hydro energy (energy of water flowing in rivers). Biomass energy and wind energy also fall in this category as these are being used since ancient times.
50. 50.  Non-conventional sources of energy : Are those which are not used as extensively as the conventional ones and meet our energy requirement only on a limited scale. Solar energy, ocean energy (tidal energy, wave energy, ocean thermal energy, OTE), Geothermal energy and nuclear energy belong to this category. These sources of energy which have been tapped with the aid of advances in technology to meet our growing energy needs are also called alternative sources of energy.
51. 51. Wind Energy: -When large masses of air move from one place to another it is referred to as wind. During this process kinetic energy gets associated with it which is referred to as wind energy. Principle of utilisation of wind energy: - Wind energy is efficiently converted into electrical energy with the aid of a windmill. A windmill is a large fan having big blades, which rotate by the force exerted by moving wind on them. These blades remain continuously rotating as long as wind is blowing and can be used to drive a large number of machines like water pumps, flour mills etc. But these days a windmill is used to generate electric current which is used for various purposes and therefore wind power stations are established all over the world which convert wind energy directly into electrical energy.
52. 52. The important uses of wind energy are; 1. It is used to drive windmills, water lifting pumps and flour mills etc. 2. It is used to propel sale boats. 3. It is used to fly engine less aeroplanes or gliders in the air. 4. It is used to generate electricity used for various purposes like lightening, heating etc.
53. 53.  Temperature- hotness or coldness of body  Thermometer-is a device used to measure temperature.  Thermal equilibrium- one system is said to be in thermal equilibrium with another system if their temperatures are the same.  Thermal energy-is the amount of energy measured with a thermometer. It represents the collective kinetic energy of the molecules moving within a substance.
54. 54.  Galelian thermometer- a glass bulb with a long stem and submerged the end of the stem in water.  Mercury thermometer  Alcohol thermometer  Bimetallic strip- two different thin strips of metal riveted together and spiraled, the outer end anchored to the thermometer case and the inner end attached to the pointer. The pointer rotates in response to change in temperature.  Optical pyrometer- measures intensity of radiation emitted by red hot or white hot substance.
55. 55.  Celsius  Farenheit  1-Kelvin  Rankine

Jan. 9, 2019
• suniza

Feb. 19, 2016

presentation on forces and motion

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