Workshop Science

Transcript

1. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-1 Workshop Science A Concise Training Module for ITI Students & Trade Apprentices. e-mail: sgjha1960@gmail.com
2. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-2 The mystery of Universe that led to the study of science.
3. Workshop Science Science is the branch of knowledge based on objectivity and involving observation and experimentation. It is the study of the natural world. Science is the systematically acquired knowledge that is verifiable. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-3
4. Workshop Science Mass & Weight You buy 1kg of sugar at Sonepat & carry it to Shimla. You will be surprise to know that it has mass of 1kg but the weight is different than what was at Sonepat. Why? The quantity of sugar has not changed means mass of any thing remains same everywhere but not weight. The SI unit of mass is kg. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-4
5. Workshop Science Mass & Weight Weight depends upon the gravitational force & gravitational force is not equal everywhere. The gravitational acceleration of our earth is 9.81 m/sec2. Weight = mass × gravitational acceleration = 75 kg × 9.81 m/sec2 = 735.75 Newton The SI unit of weight is Newton. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-5
6. Workshop Science The weight of any object 1. Depends on the mass of that planet & 2. The distance you are from the center of that planet. If your mass is 75kg then your weight on Earth - 735.75 Newton Mercury - 278.11 Newton Moon - 122.135 Newton Saturn - 673.947 Newton Sun - 19918.224 Newton July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-6
7. Workshop Science Density & Relative Density Density is the mass of a given volume of something. The density of water is 1 gram/cm3. Therefore, the mass of 1000 cm3 will be 1000 gram. 1000 cm3 is also known as 1 litre. That is why 1 litre of water is equal to the mass of 1 kg of water. The density of steel is 7.8 gram/cm3 & mercury is 13.6. Which one is heavier? July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-7
8. Workshop Science Gravity varies by altitude, latitude and local variation.On the earth's surface, the gravity will depend on the location at which it is measured. The value of gravitational acceleration varies from 9.789 m·s−2 at the equator to 9.832 m·s−2 at the poles. Objects at the equator experience a weaker gravitational pull than objects at the poles. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-8
9. Workshop Science Laws of Floatation When a body is immersed in a liquid, there are two forces acting on it. The weight W1 of the body. This is the force exerted by the earth in downward direction and Buoyancy B exerted by the liquid in the upward direction. If W > B then the body will sink. W < B then the body will float and W = B then body is in the equilibrium. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-9
10. Workshop Science Force What happens when you push the door? And what happens when you pull the door? Door may get open or even not! This is known as force. In science, force is that which changes or tends to change the state of rest or motion, rotate, or even the shape of the body. Force = mass × acceleration The unit of force in SI unit is Newton. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-10
11. Workshop Science Equilibrium July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-11 Stable equilibrium Neutral equilibrium Unstable equilibrium
12. Workshop Science Torque Torque is a rotational force. The SI unit for Torque is Newton-metre. Torque = Force × radius. How much torque is being applied on the nut when force is 20 N & radius is 0.5 m. It is 10 N-m. Yes, you are right. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-12
13. Workshop Science Lever The lever consists of a rigid rod, which can turn freely about a fixed point, known as Fulcrum. 2300 years ago, Archimedes remarked “Give me the place to stand, and I shall move the earth. In ancient Egypt, builders used the lever to move and uplift stones weighing more than 100 tons. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-13
14. Workshop Science There are three terms which we come across when discussing about lever i.e. fulcrum, load & effort. Fulcrum: The support, or point of rest, on which a lever turns in moving a body. Load : Weight to be borne or conveyed Effort : Use of physical energy. Load × Load Arm = Effort × Effort Arm July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-14
15. Workshop Science First-class levers: It is a lever in which the fulcrum is located in between the effort and the load. Examples: 1. Seesaw 2. Crowbar 3. Pliers & Scissors 4. Can opener 5. Bicycle hand break 6. Hammer July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-15
16. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-16
17. Workshop Science Second-class levers: It is a lever in which the load is located in between the fulcrum and the effort. Examples: 1. Wheelbarrow 2. Nutcracker 3. Door 4. Stapler 5. Diving board 6. Wrench July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-17
18. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-18
19. Workshop Science Third-class levers: It is a lever in which the effort is located in between the fulcrum and the load. Examples: 1. Human arm 2. Tweezers 3. Shovel 4. Broom 5. Base ball bat 6. Wrench July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-19
20. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-20
21. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-21 Identify the types of Lever?
22. Workshop Science Machines In the absence of a suitable device, many people have to be arranged to lift a motorcar so that its tyre can be changed. In order to overcome such difficulties, a few simple machines were invented, which could save the manpower i.e. single man can do the same work as many could do, though at lesser speed. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-22
23. Workshop Science The work done is the product of the force and the displacement. In science, a simple machine is any device that only requires the application of a single force to work. The force applied to the machine is known as effort. Whereas force overcome by an effort is known as load. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-23
24. Workshop Science Mechanical Advantage: The ratio of load lifted to effort applied is known as mechanical advantage. This is simply expressed in a number. Load  Mechanical Advantage =  Effort July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-24
25. Workshop Science Velocity Ratio: The ratio of distance moved by effort to the distance moved by load is termed as velocity ratio. Distance moved by effort  Velocity Ratio =  Distance moved by load July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-25
26. Workshop Science Output & Input: The product of load and distance moved by load is known as output, whereas the product of effort and distance moved by effort is known as input. Output = Load  Distance moved by load Input = Effort  Distance moved by effort. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-26
27. Workshop Science Efficiency of Machine: The ratio of output to the input of machine is known as efficiency. In simple machines the ratio of mechanical advantage to the velocity ratio is also known as efficiency of the machine. Efficiency is generally expressed %age. Output Mechanical Advantage Efficiency =  =  Input Velocity Ratio July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-27
28. Workshop Science Work, Power & Energy Work: The work is measured by the product of the force applied and the distance through which the body is displaced. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-28 Work Done = Force Applied  Distance Moved 1 joule = 1 Newton  1 meter
29. Workshop Science Power: Power of a machine is the rate of doing work. The practical unit of power is Horse Power. 1HP is the amount of work of a standard horse can do in 1 second. 1 HP (Metric) = 75 kg-m/s = 735.5 W 1 HP (British) = 550 foot pounds/s = 746 Watt 1 Watt = 1 joule/s. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-29
30. Workshop Science Energy: Energy of a body is its capacity for doing work. A system can have this energy in various forms, such as electrical, mechanical, heat, chemical, atomic energy etc. Energy of one form can be transferred to other form, but cannot be created or destroyed. If one form of energy disappears, it reappears in another form. This principle is known as law of conservation of energy. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-30
31. Workshop Science Potential Energy: Potential energy is the energy a body possesses because of its position. PE = mgh joules. Kinetic Energy: Kinetic energy is the energy a body possesses because of its motion. KE = ½mv2 joules. Remember! 1 calorie = 4.186 joule. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-31
32. Workshop Science Friction Friction is a force that resists motion between two objects in contact. Friction results in the conversion of mechanical energy into heat that serves no purpose. So is friction a necessity or an evil? Is it good or bad? Do we need it or no? Let’s find it out! July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-32
33. Workshop Science Friction is Necessary: Without friction between the feet and the ground it will not be possible to walk. In the absence of friction, the brakes of a motorcar cannot work. It is the friction between the belt and the pulley that helps in the rotation of the various parts of a machine. When the ground becomes slippery after rain, it is made rough by spreading sand etc. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-33
34. Workshop Science Friction is an Evil: Wear and tear of the machinery is due to excessive friction. A large amount of power is wasted in overcoming friction and the efficiency of the machine decreases considerably. Excessive friction between the rotating parts of a machine produces enough heat and causes damage to the machinery. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-34
35. Workshop Science Methods of Reducing Friction: 1. Polishing: Friction between two surfaces can be reduced by polishing them. 2. Ball bearings: Rolling friction is less than sliding friction. 3. Lubricants: Friction between two surfaces is decreased by lubricants.. Thin oil is used in watches. 4. Streamlining: The friction due to air is reduced by marking the automobiles streamlined. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-35
36. Workshop Science Stress & Strain Whenever a body is subjected to external load, it undergoes deformation. The resistance offered by the body to this deformation is known as the intensity of stress. Load Stress = ————— Area Its unit in SI system is N/m2. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-36
37. Workshop Science Stress & Strain External forces acting on a body brings a change in its dimensions without causing it to move. Strain is the ratio between change in dimension to its original dimension. Change in length Strain = ————————— Original length It has no unit. Why? July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-37
38. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-38 Tensile Stress Compressive Stress Shear Force
39. Workshop Science Speed & Velocity The rate at which an object is changing its place is called its speed. The speed doesn’t indicate direction. For example, a train travels 40 km in two hours then its speed will be 20 km/hour in any direction. Distance Speed = ————— Time Its unit in SI system m/s. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-39
40. Workshop Science Speed & Velocity The rate of speed of an object in a particular direction is called its velocity such as a train travels 40 km towards Delhi in two hours time then its velocity will be 20 km /hour towards Delhi. Distance Velocity = ————— Time Its unit in SI system m/s. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-40
41. Workshop Science Acceleration Consider a car to start moving from the point A. Its initial velocity is zero. After 1s its velocity is 5m/s, after 2s 10m/s and after 5s it is 25m/s. Hence, the velocity of car is increasing 5m/s in every one second. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-41
42. Workshop Science Acceleration The rate of change of velocity of an object is called acceleration. Change in velocity v - u Acceleration =  or a =  Time t Where, a = acceleration u = initial velocity v = final velocity. Its unit in SI system m/s2. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-42
43. Workshop Science Heat Heat is a form of energy, which makes us feel heat or cold. When a substance is heated or heat is taken away from it, some changes take place e.g. change is state, change in temperature, change in volume etc. Let’s take the case of water! When we heat water it changes to vapour. When we take out heat, it becomes ice! July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-43
44. Workshop Science Temperature When heat is given to a substance then it is heated and when the heat is taken out of substance then it cools down. The measure of this hotness and coldness is called temperature. Therefore, the temperature of a substance represents the degree of its coldness or hotness. Its unit in SI system is Kelvin. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-44
45. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-45 C F – 32 R K - 273  =  =  =  100 180 4 100
46. Workshop Science Boiling Point The temperature at which any substance boils & starts turning into a gas is known as the boiling point. The boiling point of water is 100C. Melting Point The temperature at which a solid melts into liquid or a liquid freezes to solid is called the melting point of that substance. The melting point of water is 0C. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-46
47. Workshop Science Transmission of Heat Heat is transferred from one place to another in three ways. Conduction - heating of iron rod Convection - heating of water Radiation - heat from sunlight July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-47
48. Workshop Science Why Mercury preferred in Thermometers? 1. It doesn’t wet the glass. No mercury is left behind in the tube, as the temperature falls. 2. It is good conductor of heat. 3. It has uniform co-efficient of expansion. 4. It remains in liquid state over a wide range of temperature. 5. Mercury melts at –39C hence, suitable for measuring low temperatures. 6. It has high density. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-48
49. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-49 Calorific value of some fuels/cereals Name Calorific Value Name Calorific Value Wood 16.7 kj/g CNG 41 kj/g Charcoal 31.4 kj/g Biogas 11.3 kj/g Alcohol 43.9 kj/g Rice 5.3 kj/g Petrol 47.7 kj/g Wheat 3.2 kj/g Kerosene 43.1 kj/g Potato 3.7 kj/g Diesel 43.9 kj/g Milk 3.0 kj/g
50. Workshop Science The unit of heat is calorie. 1 calorie is that amount of heat which can raise the temperature of 1g of water from 14.5 to 15.5 C. 1 calorie is equal to 4.2 joule. How much work can you do if you drink 5 liters of milk & eat 4 chapatis each contains 50g wheat. = (300005000) + (3200 200) joules or 15152381 calories. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-50
51. Workshop Science Atmosphere The Earth is surrounded by a blanket of air, which we call the atmosphere. It reaches over 560 km from the surface of the earth. Life on earth is supported by the atmosphere, solar energy, and our planet's magnetic fields. The atmosphere absorbs the energy from the sun, recycles water and other chemicals. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-51
52. Workshop Science There are 5 main layers of atmosphere. 1. Troposphere - up to 10 km 2. Stratosphere - up to 50 km 3. Mesosphere - up to 80 km 4. Thermosphere - up to 110 km 5. Exosphere - up to 800 km July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-52 “Aero-planes fly between Troposphere & stratosphere”
53. Workshop Science Torricelli’s experiments: Force mg AP = ---------- = -------- Area Area mgh mgh = ------------ = --------- Area  h V m  gh = ---------- = dgh V July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-53 760mm
54. Workshop Science Pressure The action of a force on unit area of the body on which it acts is termed as pressure. Its unit is N/m2. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-54 1N/m2 is equal to 1 Pascal.
55. Workshop Science Pressure July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-55 Since this unit is so small that another unit “bar” is introduced as the unit of pressure. 1 bar = 105 Pascal.
56. Workshop Science Pressure The pressure exerted by the atmosphere is known as atmospheric pressure. It is measured at the mean sea level & is expressed as;  760 mm of Hg  1.033 kgf/cm2.  1 bar or 1000 mbar.  105 Pascal.  1 atm.  760 Torr.  14.7 lb/inch2. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-56
57. Workshop Science Gauge pressure: The pressure measured by various pressure gauges. Absolute pressure: It is gauge pressure + atmospheric pressure. Vacuum pressure: Pressure below atmospheric pressure is known as vacuum pressure. Vacuum pressure = Atmospheric pressure – gauge pressure. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-57
58. Workshop Science Boyle’s law: The volume of a definite quantity of gas at a constant temperature is inversely proportional to its pressure. If 50 mL of oxygen gas is compressed from 20 bar of pressure to 40 bar of pressure, what is the new volume at constant temperature? P1 V1 = P2 V2 20 bar X 50 mL = 40 bar X V2 Solving for V2 , we get 25 mL as our answer. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-58
59. Workshop Science Charle’s Law: According to this law the volume of a definite quantity of a gas at a constant pressure is proportional to its absolute temperature. If the volume of a definite quantity of gas is V and absolute temperature is T then at a constant pressure V  T or V/T = constant. V1 / T1 = V2 / T2 July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-59 All temperatures are to be converted to Kelvin
60. Workshop Science Combined Gas Law: The mathematical expression for the combined gas law is as follows: P1 V1 P2 V2 ---------- = --------- = Constant T1 T2 A gas occupies a volume of 20 L (V1 ) at a pressure of 5 bar (P1 ) and a temperature of 500 K (T1 ). What will the volume (V2 ) be if both the pressure is raised to 10 bar (P2 ) and temperature is changed to 250 K (T2 )? July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-60
61. Workshop Science Centre of Gravity This point through which the whole weight of the body acts, irrespective of its position is known as centre of gravity (CG). July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-61 Every body has only one centre of gravity.
62. Workshop Science A number of toys are made with their base heavy by filling with clay or lead shots. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-62 When the toy is displaced, the vertical line through the new position of CG passes through the base. The equilibrium is stable and the toy returns back to its vertical position.
63. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-63
64. Workshop Science Thin Cylindrical Shells In engineering field, we daily come across vessels of cylindrical and spherical shapes containing fluids such as tanks, boilers, compressed air receivers etc. Generally, the walls of such vessels are very thin as compared to their diameters. In general, if the thickness of the wall of a shell is less than 1/10th to 1/15th of its diameter, it is known as thin shells. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-64
65. Workshop Science Whenever a vessel is subjected to internal pressure (due to steam, compressed air etc.), its wall are subjected to tensile stresses. If these stresses exceed the permissible limit, the cylinder is likely to fail in any one of the following two ways a shown. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-65
66. Workshop Science July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-66 Circumferential Stress Longitudinal Stress
67. Workshop Science Whenever a vessel is subjected to internal pressure (due to steam, compressed air etc.), its wall are subjected to tensile stresses. If these stresses exceed the permissible limit, the cylinder is likely to fail in any one of the following two ways a shown. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-67
68. Workshop Science Bending Moments & Shear Force We see that whenever a horizontal beam is loaded with vertical loads, sometimes, it bends due to the action of the loads. The beam may have one or all the three types of load. 1. Concentrated or point load. 2. Uniformly distributed load. 3. Uniformly varying load. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-68
69. Workshop Science In general, the beams are classified as under. 1. Cantilever beam. 2. Simply supported beam 3. Overhanging beam 4. Rigidly fixed or built-in-beam and 5. Continuos beam. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-69
70. Workshop Science Cantilever beam A cantilever beam which is fixed at one end and the other end is free. A is the fixed end and B is the free end. The distance from fixed end to free end is called ‘length of the cantilever.” July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-70
71. Workshop Science Simply supported beam It is a beam whose both ends are freely resting on two supports. These supports may be walls, columns etc. The horizontal distance between the two supports is called the clear span of the beam. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-71
72. Workshop Science Overhanging beam An overhang beam has both the ends projecting beyond the supports. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-72
73. Workshop Science Fixed beam A fixed beam has its both ends rigidly fixed into the supporting column, walls or beams. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-73
74. Workshop Science Continuous beam A continuous beam is supported on more than two supports. The supports at the extreme left and right are called end supports and the others are called intermediate supports. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-74
75. Workshop Science Sincere Tips 1. Define the question. 2. Gather information and resources. 3. Form hypothesis. 4. Perform experiment and collect data. 5. Analyse data. 6. Interpret data and draw conclusions. 7. Publish results. July 2004, SG Jha Training Centre OSAM India, Sonepat Slide No-75