Hi all
What comes to your mind when you think about Newton's first law of motion . Now a days it has become an obvious statement but it was not the case when the law has been formulated. Statement of Newton's first Law of motion is
" Every body continues to be in state of rest or uniform motion untill acted upon by a net external force."
Equilibrium of the bodies is the essence of the forst law of motion.
Why we have used the word net force it is because there might be more then one forces acting on the body and net force on the body is the vector sum of all the forces acting on the body. Newton's first law of motion only gives the qualitative defination of the force that is it tells us that force is only the influence behind the moving objects but it does not tell anything about what is required to keep objects moving when they are set to motion by the application of force. In out daily life we see that bodies set to motion eventualy came to rest for example book placed on a horizontal surface is pushed , it started to move and then come to rest. What does first law of motion has to explain about this effect. What would we have to do to keep the book moving ? Can first law of motion has anything to say about it. Think about it if you find any more point to discuss let me know I'll be happy to discuss
Physics Expert
For complete notes on Newton's Laws of motion visit Newton's Laws of motion
Saturday, 14 August 2010
Sunday, 1 August 2010
Work , Energy and Power (Quick Recap)
1. Work done by a constant force = F.S=FS cosθ
2. Work done by a variable force = ∫F.dS
3. If force acting on the body is along the direction of displacement of the body then work done can be calculated by calculating the area enclosed between F-S curve and displacement axis.
4. Work done by conservative forces like gravitational and electrostatic forces does not depend on the path taken by the particle and only depends on the initial and final positions of the particles.
5. Work done by non conservative forces like frictional forces are path dependent.
6. Power is the rate of doing work.
Average power = ΔW/Δt
Instantaneous power = dW/dt = F.v
7. Slope of W vs t graph gives the power of the system and area between the P vs t curve and time axis gives work done by the system.
8. Kinetic energy = (1/2)mv2
9. Gravitational potential energy = mgh where m is the mass of the object, g is acceleration due to gravity and h is the hight of object above the referance level. PE of the object is positive when object is above the refrence level and negative when it is below the refrence level.
10. An object posess kinetic energy by virtue of its motion and it posess potential energy by virtue of its position.
11. Elastic energy of a spring is given by (1/2)kx2 where k is the elastic constant for the spring.
12. Work energy theorem states that
Wext=Kf-Ki=ΔK
13. Law of conservation of energy states that " Total energy of the system always remains constant provided no external work is being done and energy of the system is not being converted to other forms of energy". Hence Energy can never be created or destroyed it can only be converted from one form of energy to another.
For full notes on Work energy and power visit the link
2. Work done by a variable force = ∫F.dS
3. If force acting on the body is along the direction of displacement of the body then work done can be calculated by calculating the area enclosed between F-S curve and displacement axis.
4. Work done by conservative forces like gravitational and electrostatic forces does not depend on the path taken by the particle and only depends on the initial and final positions of the particles.
5. Work done by non conservative forces like frictional forces are path dependent.
6. Power is the rate of doing work.
Average power = ΔW/Δt
Instantaneous power = dW/dt = F.v
7. Slope of W vs t graph gives the power of the system and area between the P vs t curve and time axis gives work done by the system.
8. Kinetic energy = (1/2)mv2
9. Gravitational potential energy = mgh where m is the mass of the object, g is acceleration due to gravity and h is the hight of object above the referance level. PE of the object is positive when object is above the refrence level and negative when it is below the refrence level.
10. An object posess kinetic energy by virtue of its motion and it posess potential energy by virtue of its position.
11. Elastic energy of a spring is given by (1/2)kx2 where k is the elastic constant for the spring.
12. Work energy theorem states that
Wext=Kf-Ki=ΔK
13. Law of conservation of energy states that " Total energy of the system always remains constant provided no external work is being done and energy of the system is not being converted to other forms of energy". Hence Energy can never be created or destroyed it can only be converted from one form of energy to another.
For full notes on Work energy and power visit the link
Wednesday, 28 July 2010
IITJEE/AIEEE test series links
hi all
Whether you are preparing for competetive exams like IITJEE/PMT/AIEEE or you are looking for some serious knowledge in physics you need to check your knowledge time to time so that you are aware of the preperation you have done . So here I am giving you the links for IITJEE/AIEEE test series in physics.Those who are not preparing for such exams can also take the test to check their knowledge. Hope they help you. So take a test of your knowledge in physics
Test series 1
Test series 2
Test series 3
Test series 4
There are three other test series available on general topics in physics for those you would have to register yourself to the
website
for further information contact mailmephysics12@rediffmail.com.
Whether you are preparing for competetive exams like IITJEE/PMT/AIEEE or you are looking for some serious knowledge in physics you need to check your knowledge time to time so that you are aware of the preperation you have done . So here I am giving you the links for IITJEE/AIEEE test series in physics.Those who are not preparing for such exams can also take the test to check their knowledge. Hope they help you. So take a test of your knowledge in physics
Test series 1
Test series 2
Test series 3
Test series 4
There are three other test series available on general topics in physics for those you would have to register yourself to the
website
for further information contact mailmephysics12@rediffmail.com.
Tuesday, 27 July 2010
Static Friction
Physics Study material for IITJEE/AIEEE/PMT In this post we tried to explain static friction which is a important concept to lern while preparing for IITJEE/AIEEE/PMT and other competetive exams. I have also given the link from where you can study the whole chapter.
-We know that frictional forces can also act between the bodies in contact with each other even if they are not moving and such type frictional force is known as static friction
-Consider a heavy metal block kept on the floor and you are trying very hard to push it to another location and you are not able to slide it even by a centimeter
-Since the block is at rest resultant force on it should be zero.To counter balance the force applied by you ,floor exerts a frictional force on the block
-Now if you begin to increase the magnitude of force gradually then bloack does not start moving until force applied is greater then a minimum value of force
-This force of static friction must be overcome by the applied force before the body at rest begin to move
-Force of friction is always equal and opposite to the external applied force as long as the body is at rest
-This means that static friction force is a self adjusting force.It adjust its value accordingly with the increase in magnitude of applied force
-This frictional force cannot be unlimited and its value cannot go beyond a maximum value fms
-This maximum value of static friction between the two surfaces in contact is known as limiting friction
-Thus magnitude of static friction can not go beyond the magnitude of the limiting friction i.e, fs <= fms
-This limiting friction is proportional to the normal contact force (N) between the bodies i.e,
fms= is proportional to N
fms=μsN
Where N =Normal contact force
μs is the proportionality constant known as coefficent of static friction
-Value of coefficent of static friction depends on the material and roughness of the surfaces of bodies in contact
-fms is the maximum value that force of static friction acting between two bodies can reach
-The actual force of static friction can be equal to zero or less then fms and its value depends on the force applied on the body thus
fs <= fms=μsN
For full notes on friction visit the link given below
link
-We know that frictional forces can also act between the bodies in contact with each other even if they are not moving and such type frictional force is known as static friction
-Consider a heavy metal block kept on the floor and you are trying very hard to push it to another location and you are not able to slide it even by a centimeter
-Since the block is at rest resultant force on it should be zero.To counter balance the force applied by you ,floor exerts a frictional force on the block
-Now if you begin to increase the magnitude of force gradually then bloack does not start moving until force applied is greater then a minimum value of force
-This force of static friction must be overcome by the applied force before the body at rest begin to move
-Force of friction is always equal and opposite to the external applied force as long as the body is at rest
-This means that static friction force is a self adjusting force.It adjust its value accordingly with the increase in magnitude of applied force
-This frictional force cannot be unlimited and its value cannot go beyond a maximum value fms
-This maximum value of static friction between the two surfaces in contact is known as limiting friction
-Thus magnitude of static friction can not go beyond the magnitude of the limiting friction i.e, fs <= fms
-This limiting friction is proportional to the normal contact force (N) between the bodies i.e,
fms= is proportional to N
fms=μsN
Where N =Normal contact force
μs is the proportionality constant known as coefficent of static friction
-Value of coefficent of static friction depends on the material and roughness of the surfaces of bodies in contact
-fms is the maximum value that force of static friction acting between two bodies can reach
-The actual force of static friction can be equal to zero or less then fms and its value depends on the force applied on the body thus
fs <= fms=μsN
For full notes on friction visit the link given below
link
Monday, 26 July 2010
IITJEE/AIEEE/PMT tips and tricke in electrostatics
1. The force with which two charges interact is not changed by the presence of the other charges.
2. Net force on any charge F=F1+F2+F3+F4+.....
3. Electric field lines extend away from the positive charge and towards thge negative charges.
4. Electric field produces the force so if a charge q is placed in the electric field E the force experience by the charge is F=qE
5. Principle of superposition also applies to electric field
so E=E1+E2+E3+E4+......
6. E is the electric field present due to all charges in the system not just the charge inside in the Gauss law.
7. Flux crossing a closed surface does not depend on the shapes and size of gaussian surface.
8. ∫E.dl over closed path is zero.
9. Electric Potential is scalar quantity.
10. Potential at point due to system of charges will be obtained by the summation of potential of each charge at that point V=V1+V2+V3+V4+..........
For more such tips and tricks click the link given below
link
2. Net force on any charge F=F1+F2+F3+F4+.....
3. Electric field lines extend away from the positive charge and towards thge negative charges.
4. Electric field produces the force so if a charge q is placed in the electric field E the force experience by the charge is F=qE
5. Principle of superposition also applies to electric field
so E=E1+E2+E3+E4+......
6. E is the electric field present due to all charges in the system not just the charge inside in the Gauss law.
7. Flux crossing a closed surface does not depend on the shapes and size of gaussian surface.
8. ∫E.dl over closed path is zero.
9. Electric Potential is scalar quantity.
10. Potential at point due to system of charges will be obtained by the summation of potential of each charge at that point V=V1+V2+V3+V4+..........
For more such tips and tricks click the link given below
link
Sunday, 25 July 2010
5 Secrets to Cracking Competitive Exams
They’re not the kind of exams you’re used to in school, but you know you have to prepare hard for them if you want to go to college. Almost every admission procedure requires that you score a certain percentage in one or more competitive exams, so unless you’re good and ready in the most efficient way possible, it’s hard to get your foot in the door that almost every other high school graduate is trying to open. If you’re looking for extra help, here are a few secrets that will help you achieve success:
• Start early: Know what you want to do before you graduate from high school and work on achieving your goal step by step. Be familiar with the requirements you must meet, the subjects you need to study, and the grades you must secure. When you begin early, you gain a head start not just on your peers, but also in your attempt to crack the exam.
• Do your research: Make a list of the colleges you want to attend and the prerequisites for admission to each of them. Don’t rely on secondhand sources for your information; instead, call the admissions office or check the official website of the institutions you’re interested in and get your queries and doubts resolved. Ask if there are any additional qualifications that you could meet in order to secure scholarships or other perks, and ensure that you send in your application well before the due date.
• Do a little everyday: Studying for an exam is a continuous process, one that must be done little by little and on a regular basis. If you try to cram everything a few days or even a few weeks before the big day, your lack of preparation is going to show you up. When it comes to competitive exams, it’s not just your grades that matter, but how well you’ve done in comparison to every other person who has taken the exam as well. And when a whole nation is competing with you, preparation is everything. So besides starting as early as you can, dedicate a few hours every day to preparing for your exam.
• Time yourself: Most competitive exams are all about time; they’re multiple choice options that have to be solved in less than a minute, and you often have just a few seconds to come up with each answer. While it’s easy to stay within the time limit for standard questions in English and other general subjects, it’s a different issue for those that involve solving mathematical or scientific equations and problems. Sometimes you get so caught up in trying to crack one equation that you neglect too many other questions in the process. So conduct as many dry runs as you can and perfect a way to answer as many questions as you can in the limited time available. Many students perform badly not because they don’t know the answers but because they do not complete the tests for lack of time.
• Stay calm and collected: Don’t panic at any stage of the exam, when preparing for it or writing it. If you’ve prepared well, your confidence should help you stay calm and collected, even when you think you’re pressed for time and the pressure starts to build. When you stick to your game plan, it’s easy to do your best.
By-line:
This article is contributed by Susan White, who regularly writes on the subject of rad tech schools. She invites your questions, comments at her email address: susan.white33@gmail.com.
• Start early: Know what you want to do before you graduate from high school and work on achieving your goal step by step. Be familiar with the requirements you must meet, the subjects you need to study, and the grades you must secure. When you begin early, you gain a head start not just on your peers, but also in your attempt to crack the exam.
• Do your research: Make a list of the colleges you want to attend and the prerequisites for admission to each of them. Don’t rely on secondhand sources for your information; instead, call the admissions office or check the official website of the institutions you’re interested in and get your queries and doubts resolved. Ask if there are any additional qualifications that you could meet in order to secure scholarships or other perks, and ensure that you send in your application well before the due date.
• Do a little everyday: Studying for an exam is a continuous process, one that must be done little by little and on a regular basis. If you try to cram everything a few days or even a few weeks before the big day, your lack of preparation is going to show you up. When it comes to competitive exams, it’s not just your grades that matter, but how well you’ve done in comparison to every other person who has taken the exam as well. And when a whole nation is competing with you, preparation is everything. So besides starting as early as you can, dedicate a few hours every day to preparing for your exam.
• Time yourself: Most competitive exams are all about time; they’re multiple choice options that have to be solved in less than a minute, and you often have just a few seconds to come up with each answer. While it’s easy to stay within the time limit for standard questions in English and other general subjects, it’s a different issue for those that involve solving mathematical or scientific equations and problems. Sometimes you get so caught up in trying to crack one equation that you neglect too many other questions in the process. So conduct as many dry runs as you can and perfect a way to answer as many questions as you can in the limited time available. Many students perform badly not because they don’t know the answers but because they do not complete the tests for lack of time.
• Stay calm and collected: Don’t panic at any stage of the exam, when preparing for it or writing it. If you’ve prepared well, your confidence should help you stay calm and collected, even when you think you’re pressed for time and the pressure starts to build. When you stick to your game plan, it’s easy to do your best.
By-line:
This article is contributed by Susan White, who regularly writes on the subject of rad tech schools. She invites your questions, comments at her email address: susan.white33@gmail.com.
Sunday, 18 July 2010
Physics questions for IITJEE, AIEEE, PMT preperation
Given below are the questions you can prepare for IITJEE-2011, AIEEE-2011 and PMT-2011 examinations. Few questions from the questions given below have been aske in previous year IITJEE, AIEEE and other such exams.
Question 1. Three capacitors of 8μF , 12μF and 24μF are connected (A) in series combination and then (B) in parallel combination . The ratio of equivalent capacitance in case (B) to that of case (A) is
(a) 11:1
(b) 1:11
(c) 1:1
(d) 3:1
Question 2. A piece of copper and a piece of germanium are cooled from the room temperature down to 80K
(a) resistance of each of them increases
(b) resistance of each of them decreases
(c) resistance of copper increases and that of germanium drcresaes.
(d) resistance of copper decreases and that of germanium increases.
Question 3. A current flows along the length of infinitely -long straight , thin walled pipe then,
(a) magnetic field at all points inside the pipe is same , but non zero
(b) the magnetic field at any point inside the pipe is zero.
(c) magnetic field is zero only on the axis of the pipe
(d) magnetic field is different at different points inside the pipe
Question 4. The line on the earth's surface joining the points where the field is horizontal is called
(a) magnetic maredian
(b) magnetic axis
(c) isogonic line
(d) magnetic equator
Question 5. The principle used in the transmission of signal through an optical fibre is
(a) total internal reflection
(b) reflection
(c) refraction
(d) dispersion
Question 6. Milikan's oil drop experiment established that
(a) electric charge depends on velocity
(b) electron has wave nature
(c) electron has particle nature
(d) electronic charge is quantized
Question 7. For steady direct current to flow in a circuit
(a) circuit must contain a source of emf
(b) charge distribution in circuit must remain unchanged
(c) lines of current density vector are closed one
(d) all of the above
I hope that these question answes will help you prepare physics for IITJEE, AIEEE and PMT exams
Answer:-
1. (a)
2. (d)
3. (b)
4. (d)
5. (a)
6. (d)
7. (d)
Question 1. Three capacitors of 8μF , 12μF and 24μF are connected (A) in series combination and then (B) in parallel combination . The ratio of equivalent capacitance in case (B) to that of case (A) is
(a) 11:1
(b) 1:11
(c) 1:1
(d) 3:1
Question 2. A piece of copper and a piece of germanium are cooled from the room temperature down to 80K
(a) resistance of each of them increases
(b) resistance of each of them decreases
(c) resistance of copper increases and that of germanium drcresaes.
(d) resistance of copper decreases and that of germanium increases.
Question 3. A current flows along the length of infinitely -long straight , thin walled pipe then,
(a) magnetic field at all points inside the pipe is same , but non zero
(b) the magnetic field at any point inside the pipe is zero.
(c) magnetic field is zero only on the axis of the pipe
(d) magnetic field is different at different points inside the pipe
Question 4. The line on the earth's surface joining the points where the field is horizontal is called
(a) magnetic maredian
(b) magnetic axis
(c) isogonic line
(d) magnetic equator
Question 5. The principle used in the transmission of signal through an optical fibre is
(a) total internal reflection
(b) reflection
(c) refraction
(d) dispersion
Question 6. Milikan's oil drop experiment established that
(a) electric charge depends on velocity
(b) electron has wave nature
(c) electron has particle nature
(d) electronic charge is quantized
Question 7. For steady direct current to flow in a circuit
(a) circuit must contain a source of emf
(b) charge distribution in circuit must remain unchanged
(c) lines of current density vector are closed one
(d) all of the above
I hope that these question answes will help you prepare physics for IITJEE, AIEEE and PMT exams
Answer:-
1. (a)
2. (d)
3. (b)
4. (d)
5. (a)
6. (d)
7. (d)
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