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Class 11 Physics – Chapter 1: Physical Quantities | Complete Handwritten Notes

PHY1011 Physics class 11 · Tribhuwan University

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📖 Class 11 Physics – Chapter 1: Physical Quantities Looking for simple, clear, and exam-friendly notes for Class 11 Physics? These handwritten notes cover Physical Quantities in an easy-to-understand format, making them perfect for quick learning and revision.

Pages
9
Academic year
2025/2026
Language
English

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Class - 11 Physics | ; 1 Phusic tities = | 2 SE S rsd | 1. Introduction 3 5. Dimensional Formulae + Physics deals with the study of nature and its laws. | + A physical quantity can be expressed | + To describe the physical world, we use certain measurable | in terms of its dimensions using a o yell emis poy ba dil igh ob wdfiy BR [Fo Eas (i) Fundamental (base) go a ERE Tr re a Ee | 6. Units and Systems of Units EE a Ph h Ee rR gre pressed pea Tuimber | measurement is called a unit. ; + System of Units: A set of units + Example: Length, mass, time, temperature, electric current etc. | used for measuring different physical 3 ¥ . p— quantities is called a system of units. 3. Fundamental and Derived Quantities « The ST (International System of Units) (i) Fundamental (Base) Quantities is the most widely used system. « These are independent quantities and cannot be expressed | o Other systems: CGS (centimetre-gram-second), in terms of other physical quantities. FPS (foot-pound -second) etc. eo There are 7 fundamental quantities in SI system. io BCS | 3. Conversion of Units 1 | Length 3 | metre mo | ghee ee = em —t- ———- unit to another, we use Epis Loreen ls Example: 1 km = 1000m |/|-#: [Electric current 5 Ll amperes cf | erate Ae || 5. | Thermodynamic temperature | T kelvin [3 [ Eee 6. | Amount of substance n mole. mol [1% | Luminous intensity Iy | candela | od 8. Significant Figures. [ S SR + The meaningful digits in a measured (ii) Derived Quantities value are called significant figures. | + These are obtained from fundamental quantities by using + The accuracy of a measurement is | mathematical relations (such as multiplication, division, indicated by. the number of significant | powers etc.). figures. {£5 Example: Velocity, acceleration, force, pressure, energy etc. + Rules for counting significant figures: 3 4. All non-zero digits are significant. 4, Dimensions of Physical Quantities GEER a + The dimensions of a physical quantity show how. it depends significant. on the fundamental quantities. 3. Leading zeros are not significant. + Tt is represented by Square brackets [ J. 4. railing 2 0 significant only if | - Example: [Length] = [L], [mass] = [M], [Time] = [T] SLE a ah Example: 2.5 (2s.f.), 0.035 (2sf), EEE I S———— {Key Points to Remember 3.00 (3 s£.), 2.30 (3s£) + Physical quantity — measurable property. + 7 fundamental quantities in SI. & TRE + Derived quantities depend on fundamental quantities. i Ane =i | + Dimensions show the dependence on base quantities. See % Phy 3 «+ ST unit is the standard unit system. cs

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1. Introduction ud Cyd 7 + pis dls ih Ody of te nd 6 lo + To describe the physical world, we use certain measurable quantities. These are called pd (i) Fundamental (base) quantities | (ii) Derived 2. Physical Quantity + A physical quantity is a property of a physical system that can be measured and expressed in a number with a unit. Example: Length, mass, time, temperature, electric current etc. 3. Fundamental and Derived Quantities (i) Fundamental (Base) Quantities in terms of other physical quantities. + There are 7 fundamental quantities in SI system. (SN. | Fundamental Quantity | Symbol | ST unit | unit Symbol 1. | Length ot metre [| 0m sl) [2] Mass. [ om | kiogam | kg | 3. | Time Fog | second | 5 | | 4. | Electric current | IT | ampere Ad [ 5. | Thermodynamic temperature | T | kelvin | kK | [ 6. | Amount of substance | nn | mole | mol | 7. | Luminous intensity | Ty | candela | cd | (i) Derived Quantities + These are obtained from fundamental quantities by using mathematical relations (such as multiplication, division,

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| Page-2 | | 4. Dimensions of Phy sical Quantities | ¢ The dimensions of a physical quantity show how it depends 1 on the fundamental quantities. : E o It is represented by square brackets [.]. SSR eh | L + Example: [Length] = [L], [Mass] = [M] , [Time] = [1] : (Some common dimensions:) — - ~ Ibe [Velocity] = [LT] 1 o [Acceleration] = [LT] | o [Force] = [MLT*] | o [Pressure] = [ML'T] . [Energy] = [MAT] {* [Power] = [MLAT3] J | « A physical quantity can be expressed in terms of its dimensions using a dimensional formula. Example: Velocity (v) = digance = [LT] ime | e Unit: A standard quantity used for measurement is called a unit. o System of Units: A set of units used for measuring different | physical quantities is called a system of units. | » The SI (International System of Units) is the most widely I= used system. + Other systems: CGS (centimetre-gram-second), FPS (foot-pound- second) etc. | * When we convert a quantity from one unit to another, | we use the conversion factor. | Example: 1 km = 1000 m & im = 10*cm

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