1. Physical Quantities and Units  9702 Physics Summary Notes
1.1 Physical Quantities
· A
physical quantity is made up of magnitude and unit
1.2 Base Units
· The
following are base units:
Quantity

Basic
Unit


Name

Symbol

Name

Symbol


Mass

Kilogram


Length

Meter


Time

Second


Temperature

Kelvin


Electric Current

Ampere


· All
units (not above) can be broken down to base units
· Homogeneity
can be used to prove
equations.
· An
equation is homogenous if base units on left hand side are the same as base
units on right hand side.
· This
may not work every time due to the fact that it does not take pure numbers into account (Ek formula)
1.3 Multiples and Submultiples
Multiple

Prefix

Symbol

10^{12}

Tera


10^{9}

Giga


10^{6}

Mega


10^{3}

Kilo


Submultiple

Prefix

Symbol

10^{3}

Milli


10^{6}

Micro


10^{9}

Nano


10^{12}

Pico

1.4 Estimations
Mass of a person

70 kg

Height of a person

1.5 m

Walking speed

1 ms^{1}

Speed of a car on the motorway

30 ms^{1}

Volume of a can of a drink

300 cm^{3}

Density of water

1000 kgm^{3}

Density of air

1 kgm^{3}

Weight of an apple

1 N

Current in a domestic appliance

13 A

e.m.f of a car battery

12 V

Hearing range

20 Hz to 20,000 Hz

Young’s Modulus of a material

Something
10^{11}

1.5 Scalar and Vector
· Scalar:
has magnitude only
e.g. speed, energy, power, work, mass, distance
· Vector:
has magnitude and direction,
can be –ve
e.g.
displacement, acceleration, force, velocity, momentum, weight, electric field
strength
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