Physics Measurements - PDF Material for SSC & RRB Exams
1. The International System of Units (SI) based on seven base units.
2. The SI Unit of length is metre (m).
3. SI Unit of amount of substance is mole
4. SI Unit of temperature is Kelvin
5. Unit of Power is Joule/sec or Watt.
6. SI Unit of electric current is Ampere
7. For measuring large distances, the light year is the used.
8. 1 light year = 9.46 × 1015m
9. 1 tonne (t) = 1000 (or 103) kg
10. Unit of Time: The SI unit of time is the second(s)
11. The ordinary mile is more precisely known as the statute mile
12. SI Unit of luminous intensity is Candela
13. Radius of the earth: 4 × 106 m.
14. The planet Mars has 1/2 the radius of the earth, the size of a geosynchronous orbit is 5 earth radii.
15. The earth-moon separation is about 60 earth radii.
16. The mean distance from the earth to the sun is called an astronomical unit.
17. An astronomical unit approximately 5 × 1011 m.
18. The star nearest the Sun, Proxima Centauri, is about 270,000 AU away.
19. To measure small lengths, we use Vernier callipers or screw gauge.
20. The unit ‘litre’ is also used to measure the volume of liquids.
21. Standard measuring vessels are used to measure volumes of liquids like milk, kerosene oil, mobile oil at petrol pumps, etc.
22. Distance is a scalar quantity
23. SI Unit of Frequency is Hertz
24. The weight may vary from place to place but the mass stays constant.
25. SI Unit of Energy is Joule
26. SI Unit of Pressure is Pascal
27. 1 parsec = 08 x 1016 = 3.26 Light year
28. 1 Horse power = 746 W
29. Our sense of touch is not always a reliable guide to the degree of hotness of an object.
30. Temperature is a measure of the degree of hotness of an object.
31. Thermometer is a device used for measuring temperatures.
32. Clinical thermometer is used to measure our body temperature.
33. The range of this thermometer is from 35°C to 42°C.
34. The range of laboratory thermometers is usually from –10°C to 110°C.
35. The normal temperature of the human body is 37°C.
36. The distance moved by an object in a unit time is called its speed.
37. Periodic motion of a pendulum has been used to make clocks and watches.
38. Motion of objects can be presented in pictorial form by their distance-time graphs.
39. The distance-time graph for the motion of an object moving with a constant speed is a straight line.
40. The shortest distance measured from the initial to the final position of an object is known as the displacement.
41. Automobiles are fitted with a device that shows the distance travelled. Such a device is known as an odometer.
42. As the object covers equal distances in equal intervals of time, it is said to be in uniform motion.
43. The tendency of undisturbed objects to stay at rest or to keep moving with the same velocity is called
44. The first law of motion is also known as the law of inertia.
45. Inertia is the natural tendency of an object to resist a change in its state of motion or of rest.
46. The mass of an object is a measure of its inertia.
47. In an isolated system (where there is no external force) , the total momentum remains conserved.
48. Heavier or more massive objects offer larger inertia.
49. Law of conservation of momentum is based on Newtons 3rd law of motion.
50. Mechanical motion is of two types, transitional (linear) and rotational (spin) .
51. The instantaneous velocity shows the velocity of an object at one point.
52. Acceleration shows the change in velocity in a unit time.
53. Force acting on an object may cause a change in its state of motion or a change in its shape.
54. When the velocity decreases the body is said to undergo retardation or deceleration.
55. Galileo was the first to find out that all objects falling to Earth have a constant acceleration of 80 m/s2 regardless of their mass.
56. The weight of a body is maximum at the poles and minimum at equator.
57. On the surface of the moon, the value of the acceleration due to gravity is nearly one-sixth of that on earth.
58. An object on the moon would weigh only one-sixth its weight on earth.
59. Force acts in the opposite direction to the way an object wants to slide.
60. Measures of friction are based on the type of materials that are in contact.
61. Concrete on concrete has a very high coefficient of friction.
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