Monday, August 10, 2015

Physical Quantities and Units | 9702 Physics Summary Notes

  • 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
m
Kilogram
kg
Length
l
Meter
m
Time
t
Second
s
Temperature
T
Kelvin
K
Electric Current
I
Ampere
A





· 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
1012
Tera
          T
109
Giga
          G
106
Mega
          M
103
Kilo
          k
Submultiple
Prefix
Symbol
10-3
Milli
          m
10-6
Micro
          μ
10-9
Nano
          n
10-12
Pico
          p

 

 

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 cm3
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  1011






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



1.6 Vectors






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