## Work, Power, Energy & Human Powered Aircraft

Human-powered aircraft require a pilot to pedal, as in a bicycle, and produce a
sustained power output of about 0.30 hp.

The Gossamer Albatross flew across the English Channel on June 12, 1979, in 2h 49 min.

(a) How much energy did the pilot expend during the flight?

(b) How many Snickers candy bars (280 Cal per bar) would the pilot have to consume to be “fueled up” for the flight?

[Note: The nutritional calorie, 1Cal, is equivalent to 1000 calories (1000 cal) as defined in physics. In addition, the conversion factor between calories and joules is as follows: 1Cal = 1000 cal = 1 kcal = 4186 J. ]

## Charge moving in a magnetic field

A particle of mass m with charge  q moving with uniform speed v normal to a uniform magnetic field describe a circular path of radius r. Derive expression for (1)time period of revolution and (11) kinetic energy of the particle.?

## Sample Question Papers, Syllabus and Guidelines for Class IX and X for Term I (First Term September’2011)

Download and practice the following question papers to score well in the CBSE Summative Assessment 1

## Force on a current carrying conductor

“if we are given an irregular shaped wire carrying current provided its cross sectional area is constant then we can find the net force on that conductor by joining the two ends of the conductor and thinking that joined part as a conductor and current should be flown in the same sequence then the force experienced by that conductor in magnetic field will give us the net force on that conductor. it is an easy method to find force on any shaped conductor……..its my own theory with some examples too”

Vishal Kumar says

What do you think?

## WHAT IS PHYSICS?

The word physics is derived from the Greek words ‘physikos’ meaning “natural” and “physis” meaning nature. So we can say that physics is the study of the natural universe dealing with the fundamental constituents of the universe, the forces they exert on one another and the results produced by these forces.

The dictionary definition of Physics is “the study of matter, energy and the interaction between them”

In Physics we study a wide range of physical phenomena spanning all length scales: from subatomic particles from which all ordinary matter is made to the behavior of the material universe.

Physics doesn’t deal with just theoretical concepts. It is applied in every sphere of human activity.

Physics is basically a problem solving discipline. It solves not only the problems – numerical and conceptual in Physics but solves many problems of our life also. Just look around the many facilities we are enjoying- the television, DVD, speakers, computer… Most of them are because of Physics. Think of it.

PHYSICS is a dynamic and exciting field of science. It is not just a collection of independent ideas, but is really an interconnected whole.

Out of the other branches of science, Physics is the most basic science; not just a part of the Physical Sciences. An understanding of Science begins with an understanding of Physics.

“There is no field in Science that speaks more intimately than Physics, of man’s speculative inquiry into the natural world” – Frederick Seitz (Rockfeller University)

Physics can be enjoyable if it is understandable

Physics is a scientrific endeavour. It is a human activity in which new ideas are constantly being tried and in which scientific truth is never absolute.

Physics is the body of knowledge about nature that represents the collective efforts, findings, insights and wisdom of the human race. It is a human activity with the functions of discovering the orderliness of nature and finding the causes that govern this order.

Why students find Physics difficult?

Just have a look at the questions commonly discussed in Physics

How did the universe begin?

How will the universe change in coming days?

What keeps the sun shining?

……… And the list of questions is endless.

If these questions fascinate you, you will certainly like Physics.

Physics can be enjoyable if it is understandable

The main reason why students look upto physics with a sense of fear is mainly due to the fact that they fail to see the big picture. This in turn is due to the fact that they study Physics not as a whole but in small chunks and many cues to the puzzle are misplaced or forgotten. To appreciate the beauty a frequent look back is required to bring the pieces together.

The students in a hurry to score marks and to complete their task of preparing for exams, they fail to enjoy the beauty and flavor. To enjoy a gfame one must understand the rules governing the game.

Physics is all around us.

Physics deals with the laws governing the nature and to enjoy life and its various activities to its fullest we must know the laws and rules of nature as well as the nature of these laws.

## Happy Family : 4 Keywords

The home should be the happiest spot we can ever know on earth. In it we have the very closest and dearest relationships, and it can be the constant source of strength and inspiration. But to create and preserve the happiness of the home requires certain qualities and attitudes which may be designated by four […]

The home should be the happiest spot we can ever know on earth. In it we have the very closest and dearest relationships, and it can be the constant source of strength and inspiration. But to create and preserve the happiness of the home requires certain qualities and attitudes which may be designated by four key words.

#### The first and most important of these is LOVE.

Ideally it is an unselfish love that brings a man and woman together to form a home, and ideally, it is love which increases that happiness of the home with children. The love which binds a family together is partly an impulse of nature, but in the Christian home, it is far more unselfish than a mere natural impulse. In Ephesians 5:25-31, the Apostle Paul says, "husbands, love your wives, even as Christ also loved the church and gave himself up for it; that he might sanctify it, having cleansed it by the washing of water with the word, that he might present the church to himself a glorious church, not having spot or wrinkle or any such thing, but it should be holy and without blemish. Even so ought husbands to love their own wives as their own bodies. He that loveth his own wife loveth himself: for no man ever hated his own flesh, but nourisheth it and cherished it, even as Christ also the church . . . For this cause shall a man leave his father and mother, and shall cleave to his wife; and the two shall become one flesh". This kind of love would lead a man to sacrifice his own pleasures, even his life, to assure the happiness and welfare of his wife. And who can doubt that the same unselfish love which a man should have for his wife, the wife should also have for her husband, and the parents should have for their children.

Unfortunately, however, love can wither and die. To keep it alive and warm requires close association, attention and care. When parents both work and have little time for their children, they become in a measure strangers to them. By nature, children love their parents and long for their parent’s love in return. Two teenagers, whose parents after work and the evening meal usually sat glued to the television till bed time, have testified that they felt so frustrated and bitter that they even wanted to put a bomb under the TV; yet they could not tell their parents how they felt. Warm personal love which expresses itself in affectionate association, care, and attention prevents such estrangement’s and bitterness, and is the single greatest source of happiness in the home. No amount of money, fast cars, gifts, and gadgets can substitute for it.

#### The second key word to happiness is FAITH:

Faith, in all its aspects trust, confidence, reliance brings happiness. If a home is to be happy parents must conduct themselves in such a way that they can have implicit faith in each other and inspire such faith also in their children. The basis of such mutual trust, however, is a faith in God and in all the attributes we associate with Him truth, integrity, fairness, compassion, mercy. If parents by their lives show their loyalty to God and his nature, they instinctively win the confidence of their children, and children likewise hold the confidence of their parents. They believe in one another.

#### The third key word to happiness is SELF-DISCIPLINE:

Self-discipline is acquired only gradually and sometimes painfully through external discipline. A generation ago we entered the age of permissiveness, when children were allowed to make their own decisions, do their own thing. Today psychiatrists are almost universally agreed that instead of making children happier, this permissiveness has been a tragedy for both children and parents. It has led to drinking, drug abuse, crime, broken homes, and an alarming increase in teen-age suicides. Until children reach enough maturity in judgement and character to administer self-discipline, they must be guided by their parents. In Ephesians 6:1-3, the Apostle Paul says, "Children obey your parents in the Lord: for this is right. Honor thy father and thy mother (which is the first commandment with promise) that it may be well with thee, and that thou mayest live long on the earth". Obedience implies definite restrictions. Parents must emphasize with children that some things are right and some things are wrong, and must see that their children observe the limitations. But when instruction fails and discipline seems necessary, it must never be done through frustration or anger, but always with love. The apostle says in Ephesians 6:4, that -fathers are not to provoke their children to wrath, but nurture them in the chastening and admonition of the Lord. If this is done right, children actually love and respect their parents more, for they realize their parents love them enough to worry over and correct them. As the writer of Hebrews says in Chapter 12:9, our fathers chastised us, and instead of being estranged we "gave them reverence". Thus, chastening one in the right way may for the moment seem "grievous", yet the writer says it "yields peaceable fruit to them that have been exercised" by it (Chapter 12, verse 11).

#### The fourth, key word to happiness is RESPONSIBILITY:

Responsibility grows naturally out of the first three. If a home is filled with love, with mutual confidence and trust, and has had the guidance and correction necessary to develop self-discipline, the natural result is a recognition of responsibility. Each member of the family feels a responsibility to the others, a responsibility to merit confidence and truth, a responsibility to keep one’s promises, to carry out duties and assignments. As this sense of responsibility becomes a habit, it carries over to those outside the family, to employers, associates, and friends.

When the members of a family have little or no confidence in each other, when they can seldom depend on their doing what they are supposed to do, you have the making of inevitable unhappiness and tragedy. But when the members of a family have full confidence in each other, and when through self-discipline they have formed the habit of responsibility, you have the sure foundation, not only of a happy family, but of successful lives.