Physical quantity
Measuring instrument
Length
Ruler, meter tape
Time
Digital watch
Temperature
Thermometer
Weight
Weighing scale
Basic quantity
SI unit
SI unit symbol
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
Temperature
Kelvin
K
Current
Ampere
A
Amount of substance
Mole
Mol
Luminous intensity
Candela
cd
Derived quantity
SI unit symbol
Area
m2
Volume
m3
Velocity
ms-1
Acceleration
ms-2
Density
kgm-3
Basic quantity
Basic quantity unit
Dimension symbol
Length
m
[L]
Time
s
[T]
Mass
kg
[M]
can check either any equation is correct/valid or not
Rule 1: the quantities the only can be added or subtracted if it have same dimensions.
Rule 2: any equation only valid/correct if the dimensions of the quantities on each side are same.
Values
Scientific notation term
Prefixes term
2000 m
2 x 103 m
2 km
0.005 m
5 x 10-3 m
5 mm
45 000 000 bytes
45 x 106 bytes
45 Mbytes
0.00000008 s
80 x 10-9 s
80 ns
0.2 A
200 x 10-3 A
200 mA
1 km
1000 m
1m
100 cm
1 kg
1000 g
1 hour
60 min
1 hour
3600 sec
Example The total length of the Penang bridge is 13.50 km making it the second longest bridge in Malaysia and the fifth longest in South East Asia.
Convert this length of the bridge to cm.
Solution
Given the length of bridge is 13.50 km. Convert 13.50 km to cm. 1 km = 1000 m
1 m = 100 cm
13.50 km =
13.50 đ?‘˜đ?‘š 1
1000 đ?‘š 1 đ?‘˜đ?‘š
= 13500 m
13500 m =
13500đ?‘š 1
100 đ?‘?đ?‘š 1đ?‘š
= 1350000 cm = 1.35 X10 6 cm