بوابة مدرسة طوخ دلكة الثانوية

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 Main concepts:-

اذهب الى الأسفل 
كاتب الموضوعرسالة
mido

mido

عدد الرسائل : 4
العمر : 22
رقم العضوية : 49
تاريخ التسجيل : 28/01/2009

مُساهمةموضوع: Main concepts:-   الأربعاء يناير 28, 2009 2:27 pm

Main concepts:-
1- Physics: is the science concerned with the study of particles and waves, its is an experimental science.

2- Basic physical quantities which cannot be drived one form the other as distance (or length) , mass, time electric charge and temperature.

3- Derivable physical quantities: they can be drived from the basic physical quantities (e.g): speed acceleration, force, energy, work, power, electric current, voltage, electric resistance, capacitance etc

. 4- Units: every physical quantity (basic or derived) has units, these units obey an iternational metric system of units (e.g) distance is measured in meter (m) , mass in kilogram (kg), time in second (s), charge in Coulomb , force in Newtin (N) energy or work in Joule (J), current in Ampere (A), voltage in volte (V), capacitance in farad (F) resistance in Ohm (W).

5- Standard units: every unit of measurable quantities has a standard reference kept in calibration labs, which are known by precision and stability.

6- The unit of time (second) is calibrated againest a cesium atomic clock, whose accuracy is of second.

7- The standard kilgram is calibrated against a cylinder of platinum and iridum of definite size at 0o c kept in Paris and elsewhere.

8- Process of measurments: is performed using pre-calibrated instruments, whose accuracy has been checked internationally.

9- Analog, measuring instruments use pointer, others are digital, some depend on direct reading such as measuring tape.

10- Accuracy and Error: No measurment can be done with 100% accuracy, there is always error. This error might be due to instrument e.g an aging battery, or due to human error in reading, or due to environmental conditions (temp. humidity ….etc)

11- The language of physics: physics expresses the relation between physical quanties in the form of mathematical formulas or equation, which have physical meaning, which translate what exists in nature.

12- Physical constants: There are physical quantites which represent fixed relations between certain quantities or constants, which do not change from an experiment to another some have units , some do not i.e ratios.

13- Power of 10: we may express large quantities as 100000 as 105. Also, small quantities as 0.0001 as 10-4. In mainpulation we have 105 x 10-4 and . we call smaller units special names, such as m is centimeter (cm), m is millimeter (mm) is micrometer (mm). These are called prefixes.
This must be taken into account in conversion. e.g. 1mm = 10 -3 m etc.

14- Numerical sense: While solving equation of physics we must have awareness of numbers, we cannot depend blindly on the calculator and stop thinking, we need to develop the intuition or logic called "common sense" e.g. we can not accept the answer to the distance between Cairo and Alex. As 3 x 10-5m.

15- Approximation: we may approximate the results in ordinary calculations if we have for example a value of 6.343212153 it may be approximated to 6.34 or 6.343 or 6.3 deppending on the limit of approximation accepted (tolerence). But when using measuring instruments we obtain results experimentally as precise only as thes measuring instrumens allow.

16- A scaller physical quantity is that quantity that is well defined by its magnitude only.

17- A vector physical quantity is that quantity that is well defined by its magnitude and direction.

18- We denote the vectore as and the magnitude of the vector as . The arrow denotes that the quantity is a vector meaning that it has magnitude and direction. The two short upright bars (read modulus) denote, the magnitude of the vector.

19- Greek letters: we use symbols to denote physical quantities, but soon we run out of letters, we often use Greek alphabet.

20- The visible and invisible: Not being able to see an object does not mean that it does not exist. e.g. we can not see an electron but we can detect it from its effects. Physics is an accumulation of expertise.

21- Cheer up: During the study of physics we must develop the sense that what we learn is our asset, which may be able to use in practice. This feeling when reachs the level of cherishing physics, will end up in discovery and invention and will demand of us always to ask ourselves two questions "how and why?"
الرجوع الى أعلى الصفحة اذهب الى الأسفل
معاينة صفحة البيانات الشخصي للعضو
ma7moud 3omar

ma7moud 3omar

عدد الرسائل : 114
العمر : 25
رقم العضوية : 45
تاريخ التسجيل : 26/01/2009

مُساهمةموضوع: risk   الجمعة يناير 30, 2009 7:47 pm

great cheers cheers
الرجوع الى أعلى الصفحة اذهب الى الأسفل
معاينة صفحة البيانات الشخصي للعضو
adham

adham

عدد الرسائل : 193
العمر : 25
الموقع : طوخ
رقم العضوية : 36
من مواضيعي : أجمل الألعاب
اللوح المحفوظ
أجزاء spiderman

تاريخ التسجيل : 31/12/2008

مُساهمةموضوع: رد: Main concepts:-   الجمعة يناير 30, 2009 8:04 pm

والله ياد يا محمود إنت 100 100
الرجوع الى أعلى الصفحة اذهب الى الأسفل
معاينة صفحة البيانات الشخصي للعضو
محمد فتح الله

محمد فتح الله

عدد الرسائل : 39
العمر : 25
رقم العضوية : 5
تاريخ التسجيل : 10/12/2008

مُساهمةموضوع: رد: Main concepts:-   الجمعة يناير 30, 2009 8:11 pm

والله الرجال ده بيتكلم كلام مظبوط
الرجوع الى أعلى الصفحة اذهب الى الأسفل
معاينة صفحة البيانات الشخصي للعضو
 
Main concepts:-
الرجوع الى أعلى الصفحة 
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