O Level Physics Chapter : Physical Quantities and Units

Prepared By: Shakil Raiman

0.1: Physical Quantities and Units

There are two kinds of physical quantities 1. Base Physical Quantities 2. Derived Physical Quantities

0.2: Base Physical Quantities and Units

Base Physical Quantities SI Units Symbol for Units

Length meter m

Mass kilogram kg

Time second s

Current Ampere A

Temperature Kelvin K

Amount of substance mole mol

Luminous Intensity candela cd

0.3.1: Derived Physical Quantities and Units

Derived Physical Quantities

SI Units Symbol for Units

Speed, Velocity meter/second ms-1

Acceleration meter/second2 ms-2

Force, Weight newton N

Volume meter3 or cm3 m3 or cm3

Density kilogram/meter3 kgm-3 or gcm-3

Momentum kilogram-meter/second kgms-1

Moment newton-meter Nm

0.3.2: Derived Physical Quantities and Units

Derived Physical Quantities

SI Units Symbol for Units

Work Done, Energy Joule J

Power Watt W

Pressure newton/meter2, Pascal Nm-2, Pa

Charge Coulomb C

Potential Difference Voltage V

0.4: PrefixesPrefix Symbol Exponent

Tera T 1012

Giga G 109

Mega M 106

kilo k 103

Deci d 10-1

Centi c 10-2

Milli m 10-3

Micro 10-6

Nano n 10-12

0.4.1: Use of Prefixes

1 km = 1000 m 50 MW = 50 000 000 W 1 mm = 0.001 m 1 GHz = 1 000 000 000 Hz 32 GB = 32 000 000 000 B (approximately)

0.5: Scalar and Vector Quantities

Scalars VectorsDefinition A scalar is a quantity having

magnitude (size) onlyA vector is a quantity having

both magnitude and direction.

Operation Scalar can be added or subtracted simply

Vectors can be added or subtracted graphically.

Example distance, mass, length, time, volume, density, energy, speed, power,

temperature etc.

displacement, force, weight, moment etc.

0.5.1: Calculation Scalar and Vector Quantities

Scalar: Simple addition or substruction. Example: 5kg + 3 kg = 8 kg 20 J + 60 J = 80 J

Vectors: Vector can be added to form a RESULTANT. a. Simple algebraic addition when the vectors are parallel

Example: 5 N (right) + 15 N (right) = 20 N (right) 15 N (right) + 5 N (left) = 10 N (right)

b. Parallelogram addition when the vectors are not in the same straight line.

Example: 6 N acting East and 8 N acting West. So 10 N acting. Check on board.

Thank You All

Wish you all very good luck and excellent result.