Chapter 1 Form 4 - Tutorial 1 (Physics)
Based Quantity and Derived Quantity
1. A physical quantity is a quantity that can be measured
2. A base quantity is a physical quantity that cannot be defined in terms of other physical quantities.
Base Quantity
|
SI Unit
|
Symbol
|
Mass, m
|
Kilogram
|
kg
|
Length, l
|
Meter
|
m
|
Time, t
|
Second
|
s
|
Temperature, T
|
Kelvin
|
K
|
Current, I
|
Ampere
|
A
|
Table 1.1
3. Table 1.1 shows the five base quantity with their respective SI units. (MLTTC)
4. A derived quantity is a combination of various basic quantities. Units for derived quantities are known as derived units.
Derived Quantity
|
Relationship with the base quantity
|
Derived Unit
|
Volume
|
Length(m) x Breadth(m) x Height(m)
|
m3
|
Density
| (Mass(kg))/(Volume(m^3)) |
kg m-3
|
Acceleration
| (Change in Velocity(〖m s〗^(-1)))/(Time Taken(s)) |
m s-2
|
Velocity
| (Displacement(m))/(Time(s)) |
m s-1
|
Momentum
|
Mass(kg) x Velocity(m s-1)
|
kg m s-1
|
Force
|
Mass(kg) x Acceleration(m s-2)
|
kg m s-2 (N)
|
Impulse
|
Change of Momentum
(kg m s-1)
[ Ft=m(v-u) ]
|
kg m s-1 (N s)
|
Energy
|
Force(kg m s-2) x Displacement(m)
|
kg m2 s-2 (J)
|
Power
| (Energy(kg m^2 s^(-2)))/(Time(s)) |
kg m2 s-3 (W)
|
Table 1.2
5. Table 1.2 show a list of derived quantity and their respective derived units.
6. For easier recording and comparison, very large or very small measurement of physical quantities are represented by prefixes as shown in Table 1.3 below.
Prefix
|
Symbol
|
Value
|
Standard form
|
10n where n is
|
Example
|
Tera
|
T
|
1 000 000 000 000
|
1012
|
12
|
Tetrameter (Tm)
|
Giga
|
G
|
1 000 000 000
|
109
|
9
|
Gigabyte (GB)
|
Mega
|
M
|
1 000 000
|
106
|
6
|
Megawatt (MW)
|
Kilo
|
K
|
1 000
|
103
|
3
|
Kilojoule (kJ)
|
Hecto
|
h
|
100
|
102
|
2
|
Hectometre (hm)
|
Deca
|
da
|
10
|
101
|
1
|
Decasecond (das)
|
Deci
|
d
|
0.1
|
10-1
|
-1
|
Decimetre (dm)
|
Centi
|
c
|
0.01
|
10-2
|
-2
|
Centimetre (cm)
|
Milli
|
m
|
0.001
|
10-3
|
-3
|
Milliampere (mA)
|
Micro
|
µ
|
0.000001
|
10-6
|
-6
|
Microsecond (µs)
|
Nano
|
n
|
0.000000001
|
10-9
|
-9
|
Nanometre (nm)
|
Pico
|
p
|
0.000000000001
|
10-12
|
-12
|
Picometre (pm)
|
Table 1.3
A x 10n
Where 1 < A < 10 and n = integer. The magnitude should always be rounded to 3 or 4 significant numbers/figures.
Conversion of Units
1m = 100 cm (102 cm) 1 cm = 0.01 m (10-2 m)
1m2 = 10 000 cm2 (104 cm2) 1 cm2 = 0.0001 m2 (10-4 m2)
1m3 = 1 000 000 cm3 (106 cm2) 1 cm3 = 0.000001 m3 (10-6 m3)
1kg = 1 000 g (103 g) 1 g = 0.001 kg (10-3 kg)
1 hour = 3 600 s (3.6x103 s) 1 s = 1/3600 hour
1 km = 1 000 m (103 m) 1 m = 0.001 km (10-3 km)
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