Dr Vince's Physics Notes

MCQ. In a typical power station, amid a series of energy transfers and conversions, about 70% of energy input gets wasted in form of thermal energy, efficiency of such a power station is about

0.3
0.4
0.7
1

MCQ. Output of a truck is 4500 J and its efficiency is 50%, input energy provided to truck is

5000 J
900 J
9000 J
500 J

https://m.facebook.com/story.php?story_fbid=1381655178619569&id=100003253001346

Gr09_Ch05W.mp3 Shared with Dropbox

Did Newton himself find the gravitational constant, G?
The gravitational constant is the proportionality constant used in Newton’s Law of Universal Gravitation, and is commonly denoted by G.
Although the gravitational constant was first introduced by Isaac Newton as part of his popular publication in 1687, the Philosophiae Naturalis Principia Mathematica, it was not until 1798 that the constant was observed in an actual experiment. Don’t be surprised. It’s mostly like this in physics. The mathematical predictions normally precede the experimental proofs.

Anyway, the first person who successfully measured it was the English physicist, Henry Cavendish, who measured the very tiny force between two lead masses by using a very sensitive torsion balance. It should be noted that, after Cavendish, although there have been more accurate measurements, the improvements on the values (i.e., being able to obtain values closer to Newton’s G) have not been really substantial.
http://www.universetoday.com/34838/gravitational-constant/
http://www.physicsclassroom.com/class/circles/Lesson-3/Cavendish-and-the-Value-of-G

What is the Gravitational Constant? - Universe Today The gravitational constant is the proportionality constant used in Newton’s Law of Universal Gravitation, and is commonly denoted by G. This is different from g, which denotes the acceleration due to gravity. In most texts, we see it expressed as: G = 6.673×10-11 N m2 kg-2 It is typically used in th...

Space Suits

Three modes of heat transfer

Critical Angle

Plane mirror

Thermometer

Grade 10 Power

Grade 10 Manometer

Grade 9 Physics

Grade 9 Physics Quiz

26 Which statement is correct?
A Gamma rays have a longer wavelength than ultra-violet waves.
B Infra-red waves have a lower frequency than radio waves.
C Microwaves have a longer wavelength than visible light.
D X-rays have a higher speed in air than visible light.

28 Which statement about the speed of
A sound travels fastest in a vacuum
B sound travels fastest in gases
C sound travels fastest in liquids
D sound travels fastest in solids

30 A piece of wire has a resistance of 16Ω. Another wire made from the same metal has four times the length and twice the cross-sectional area. What is the resistance of the wire?
A 8Ω B 32Ω C 96Ω D 128Ω

GCE Quiz for Grade 10 Physics

March လ တစ္လ သင္လိုက္တဲ့စာက ဧၿပီလမွာ ပိတ္ၿပီး ျပန္လာေတာ့ ဘာမွ ျပန္ပါမလာဘူး။ ဧၿပီထက္ဆိုးတာ ေအာက္တိုဘာ၊ ေက်ာင္းစီးရီးေယာင္ေယာင္ ဝိုင္းစီးရီး ေယာင္ေယာင္၊ အ႐ွိန္နဲ႔ေလွာ္တက္ရမဲ့ ေရဆန္ကို ရပ္ၿပီးမ်ား နားေနရဲေသးတယ္လို႔။

Answers for Chapter 1 True/False
1 False
2 True
3 True
4 True
5 True
6 True
7 True
8 True
9 True
10 False
11 False
12 True
13 True
14 False
15 False
16 False
17 True
18 True
19 True
20 False
21 True
22 False
23 True
24 True
25 True
26 True
27 True
28 False
29 True
30 True
31 True
32 True
33 False
34 False
35 True
36 True
37 False
38 False
39 False
40 True
41 True
42 True
43 True
44 False
45 False
46 False

Questions B: Say True (or) False.
1. A lever generates a turning effect when a force is applied at the pivot.
2. A machine of high power should be used if a lot of work has to be done quickly.
3. A man is able to produces a power of 1000 W only for a short duration.
4. A perfect machine is one for which whose efficiency is 1.
5. A perfect machine is one for which output work is equal to input work.
6. Efficiency is a technical term derived from everyday usage.
7. Efficiency is dimensionless (unitless).
8. Efficiency of a machine is always less than 100%.
9. Elastic limit is different for different elastic bodies.
10. Elastic limits of different bodies are the same.
11. Energy and power have the same units.
12. In using a machine, the heavy load moves through a small distance
13. In using a machine, the small effort applied will have to move through a large distance
14. It is possible, in practice, to build a perfect machine.
15. Knowing amount of work done is always more important than knowing rate of doing work.
16. Large machines are made up of small machines.
17. Matter is a scalar quantity.
18. Power is a concept used in mechanics.
19. Power is a scalar quantity.
20. Power is more fundamental than energy.
21. Power is not a fundamental concept of physics.
22. Power is the product of force and speed.
23. Power is very useful in practice.
24. Pressure is a scalar quantity.
25. Rubber bands have elastic property.
26. Springs have elastic property.
27. The force applied to an elastic body is called stress.
28. The graph of strain vs stress is always a straight line.
29. The mechanical advantage has no unit.
30. The mechanical advantage of a machine may be equal to 1.
31. The potential energy can be transformed into electrical energy.
32. The power is the product of force to velocity.
33. The product of force and distance traveled is work.
34. The ratio of input work to output work is efficiency.
35. The ratio of the stress to the strain is constant.
36. The SI unit of power is the watt.
37. The strain is always proportional to the stress.
38. The strain produced is always proportional to the stress causing it.
39. The unit watt is the same as joule per coulomb.
40. The Velocity Ratio is usually greater than Mechanical Advantage.
41. Threads have elastic property.
42. Water in a dam has potential energy.
43. Work done is the energy transferred in any system where a force causes movement.
44. Work is a vector quantity.
45. Work is the product of force and distance.
46. Work may be defined as the product of force applied and distance.

Answers for Chapter 1 Fill in the Blanks
1 brake system of a car
2 increases in potential energy
3 increases in kinetic energy
4 foot-pound per second
5 (elastic) potential
6 Work done
7 inclined plane
8 550 foot-pounds
9 horse power (hp)
10 erg per second
11 horse power
12 hydraulic System
13 friction present
14 joule per second
15 displacement
16 The watt
17 Machines
18 746 × 107
19 larger
20 lever
21 machine
22 perfect
23 efficiency
24 Hooke’s
25 average
26 stress
27 strain
28 perfect
29 1 joule
30 1 erg
31 1 watt
32 7 W
33 machine
34 effort
35 impossible
36 perfect
37 simple
38 load
39 watt
40 550
41 746
42 106
43 107
44 velocity
45 power
46 elasticity
47 lever
48 strain
49 joule
50 stress
51 effort
52 work done
53 velocity
54 power
55 efficiency
56 efficiency
57 constant
58 watt
59 newton
60 joule
61 power
62 watt (W)
63 foot-pound
64 one watt
65 1
66 input work
67 output work
68 output work
69 input work
70 746
71 elongated
72 stress

CHAPTER 1: WORK DONE AND POWER
Questions A: Fill in the blanks.
1. ________ is an example of hydraulic press.
2. In lifting a load to a vertical height, the work done is equal to ________.
3. In speeding an object horizontally, the work done is equal to ________
4. In the British system the unit of power is ________.
5. A wound clock spring has the ________ energy.
6. ________ is the energy transferred in any system where a force causes movement.
7. A screw jack is an example of ________.
8. If the work done in 1 second is ________, the power is 1 horse power (hp).
9. In the British system, the power of machines are expressed in ________
10. In the CGS system, the unit of power is ________.
11. In British engineering system, the powers of engines are also expressed in ________.
12. The ________ transfers force from place to place using fluids.
13. The Mechanical Advantage of a machine depends on ________.
14. The unit watt is the same as ________
15. Work is the product of force and ________.
16. ________ is the unit of power equal to a rate of energy transfer of 1 joule per second.
17. ________ transmit force from one point to the next.
18. 1 hp is equal to _________ erg s-1.
19. 1 kW power is ________ than l hp.
20. A ________ generates a turning effect if a force is applied at some point other than the pivot.
21. A ________ is an appliance that enables work to be done.
22. A ________ machine is one for which output work is equal to input work.
23. A perfect machine is one for which whose ________ is 100 %.
24. A spring obeys ________ law.
25. Calculated power obtained by using P = W/t is only the ________ power.
26. Hooke called the applied force the ________.
27. Hooke called the elongation the ________.
28. If a machine is ________ the mechanical advantage will be equal to the velocity ratio.
29. If the work done in 1 second is ________ the power is 1 watt.
30. If the work done in 1 second is ________, the power is 1 erg per second (erg s-1)
31. If the work done in 1 second is 1 joule, the power is ________.
32. If the work done in 9 s is 63 J, the power is ________.
33. In lifting a large load, a ________ is employed.
34. In using a machine, some of the ________ is spent in overcoming frictional force present.
35. It is ________, in practice, to build a perfect machine.
36. It is impossible, in practice, to build a ________ machine.
37. Large machines are made up of ________ machines.
38. Mechanical advantage is the ratio of the ________ to the effort.
39. One ________ equal to a rate of energy transfer of 1 joule per second.
40. One horse power is equal to ________ foot-pounds per second.
41. One horse power is equal to ________ watt.
42. One megawatt is equal to ________ watt.
43. One watt is equal to ________ erg per second.
44. Power is the product of force and ________.
45. The ________ is the product of force to velocity.
46. The ability to retain the original form is called ________.
47. The crowbar is an example of ________.
48. The elongation produced by an elastic body is called ________.
49. The energy may be given in terms of ________ [or the electron volt]
50. The force applied to an elastic body is called ________.
51. The mechanical advantage of the machine the ratio of a load to ________.
52. The product of force and displacement is the ________
53. The product of the force applied and the ________ can be expressed as power.
54. The rate of doing work is ________.
55. The ratio of output power to input power may be defined as the ________ of the machine.
56. The ratio of output work to input work is defined as the ________ of the machine.
57. The ratio of the stress to the strain is ________
58. The SI unit of (mechanical) power is ________
59. The SI unit of force is ________ (OR) The unit for force in SI is ________
60. The unit ________ is the same as newton metre.
61. The unit kilowatt is the unit of ________.
62. The unit of power in SI system is the ________.
63. The unit of work done in British system is ________.
64. The unit one joule per second is equivalent to ________.
65. The velocity ratio is usually much greater than ________
66. The work done by the effort is called the ________.
67. The work done on the load is called the ________.
68. The work obtained from the machine is called ________.
69. The work supplied to the machine is called ________.
70. There are ________ W in 1 hp.
71. If a small load is applied to a free end of a suspended spring, the spring is stretched or ______.
72. Within elastic limits ________ is directly proportional to strain.

Direction of electric field.

၁၀၀ ရသြားတဲ့ သူေတြအားလံုးက လူေတာ္ေတြသာျဖစ္တယ္။ ၾကဳိးစားတဲ့သူေတြျဖစ္တယ္။ လူညံ့ေတြ လူပ်င္းေတြကို ၁၀၀ ရေအာင္ မလုပ္ေပးႏိုင္ခဲ့ဘူးသလို လုပ္ေပးႏိုင္တဲ့ တန္ခိုးလည္း မ႐ွိဘူး။ ေတာ္တဲ့သူတိုင္းလည္း ၁၀၀ မရဘူး။ ၁၀၀ ရတဲ့သူေတြရဲ႕ ထူးျခားမႈ ဆိုလို႔ ႐ိုေသေလးစားမႈ ၁၀၀ %၊ ေျပာစကား နားေထာင္ျခင္း ၁၀၀ %၊ ခိုင္းတဲ့အလုပ္ ရာႏႈန္းျပည့္နီးပါးလုပ္ျခင္းတို႔ ႐ွိပါတယ္။ ၁၀၀ ရသြားတဲ့သူေတြေကာ ဆရာခိုင္းထားတာေတြ ပ်က္ကြက္မႈ မ႐ွိဘူးလားဆိုရင္၊ ႐ွိတယ္၊ ဒါေပမဲ့ ခိုင္လံုတဲ့ လက္ခံႏိုင္တဲ့ အေၾကာင္းျပခ်က္႐ွိတယ္။ ဆရာကို မေထမဲ့ျမင္ ပ်က္ကြက္မႈမ်ဳိး၊ ငါေတာ္တယ္ ငါ့နည္းငါ့ဟန္ လုပ္တတ္တယ္ ဆိုၿပီး ပ်က္ကြက္မႈမ်ဳိးေတာ့ မ႐ွိဘူး။ ခိုင္းတာမလုပ္တတ္တဲ့လူမ်ဳိးက ခိုင္းတတ္တဲ့ ဆရာမ်ဳိးနဲ႔ အဆင္မေျပႏိုင္ဘူး။ အမွတ္ ဘယ္ေလာက္ရရ ေက်နပ္ႏိုင္သူမ်ဳိးကလည္း အျမဲ အမွတ္ မ်ားေနေစခ်င္တဲ့ ဆရာမ်ဳိးနဲ႔ အဆင္မေျပႏိုင္ဘူး။ ပံုမွန္အလုပ္လုပ္မွ အမွတ္မ်ားမယ္လို႔ အစြဲႀကီးတဲ့ ဆရာမ်ဳိးကို ေ႐ွာင္ပါမွ သင္သက္သာမွာပါ။ ကံတရားက သင့္ဖက္မွာ ႐ွိေနပါေစ။

ၾကဳိးစားေနၿပီလား။ တကယ္ေျပာေနတာလား။ ဒါဆိုရင္
၁။ မင္းမွာ တစ္ပါတ္စာ Master Time-table ႐ွိသလား။
၂။ မင္းမွာ ဒီေန႔ လုပ္စရာ Detailed plan နာရီတိုင္းမိနစ္တိုင္းအတြက္႐ွိသလား။
၃။ မင္းဟာ အဲဒီ plan ေတြ ျဖစ္ေအာင္ လုပ္သလား။
အဲဒီလိုေတြ မ႐ွိပဲ ၾကဳံသလို အဆင္ေျပသလို လုပ္ေနတယ္ ဆိုရင္ေတာ့ မင္းၾကဳိးစားတယ္ဆိုတာ ယံုေပးပါမယ္၊ မင္းေအာင္ျမင္မယ္လို႔ေတာ့ ငါမေမွ်ာ္လင့္ပါဘူး။