CHAPTER 1 PHYSICS NOTES FULL COMPLETE PPTX

PHYSICS NOTES

1. 1.3 Physical Quantities 1.3 Physical Quantities
and Their Unitsand Their Units

2. 1.3 Physical Quantities and Their
Units
1.A physical quantities is a quantity which
can be measured.
2.There are five physical quantities which
are frequently used in measurement
length
mass
time
temperature
electric current

3. 3.Physical quantities are measured in the
International System of Units (SI units). SI
units are used as standard units all over the
world.
Physical
Quantity
SI unit symbol Measuring
Instrument
Length metre m Metre rule
Mass kilogram kg Lever balance/
beam balance
Time second s Stopwatch
Temperature Kelvin K Thermometer
Electric Current ampere A Ammeter

4. 4.The value of a quantity can be written with a prefix. Each prefix has its own symbol
and value. Prefixes are used in the SI unit to state a very small or very big value.
Prefix Symbol Numerical Value Multiplying
factor
Giga G 1 000 000 000 x 10
9
Mega M 1 000 000 x 10
6
Kilo k 1 000 x 10
3
Deci d 0.1 x 10
-1
Centi c 0.01 x 10
-2
Milli m 0.001 x 10
-3
Micro  0.000 001 x 10
-6
Nano n 0.000 000 001 x 10
-9

5. 5.We write values with prefixes to make it easier to record
physical quantities.
Quantity Prefixed form
0.3 m 0.3 m = 3 x 0.1 m
= 3 x 10
-1
m
= 3 dm
(deci has the value of 0.1)
45 000 g45 000 g = 45 x 1000 g
= 45 x 10
3
g
= 45 kg
(kilo has the value of 1000)
0.0025 A0.0025 A = 2.5 x 0.001 A
= 2.5 x 10
-3
A
= 2.5 mA
(milli has the value of 0.001)

6. 6.There are many physical quantities.
Length, mass, time, temperature and
electric current are only five out of
the seven basic quantities. All other
quantities such as area, volume,
density and velocity are obtained by
multiplying or dividing two or more
basic quantities.
For example, area = length x width.

7. HOW TO USE PREFIXES IN A
MEASUREMENT
7 000 000 W = 7 W X 1 000 000
= 7 MW
0.000 002 S = 2 s X 0.000 001
= 2 µs
0.006g = 6 g X 0.001
= 6 mg

8. STANDARD
FORM
: - numerical representation in multiplier factors
Written as follows :
A x 10
n
with 1 ≤ A ≤ 10
and n is the integer
Example of standard forms in measurement :
Value of
physical
quantities
Normal Form Standard Form Prefix Form
5 000 m 5 X 1 000 m 5 X 10
3
5 km
8 000 000 m 8 X 1 000 000 m8 X 10
6
8 Mm
0.002 m 2 X 0.001 m 2 X 10
-3
2 mm

9. Exercise
Exe 1.4 (Textbook pg 17)
Q2.
a)0.08m = 8 x 0.01 m
= 8 x 10
-2
m
= 8 cm
b) 6 000g = 6 x 1000 g
= 6 x 10
3
g
= 6 kg
c) 0.007 A = 7 x 0.001 A
= 7 x 10
-3
A
= 7mA
d) 5 500m = 5.5 x 1000 m
= 5.5 x 10
3
m
= 5.5 km
e) 0.009m = 9.0 x 0.001 m
= 9 x 10
-3
m
= 9 mm

10. Reinforcement Exercise
1. Convert the following values into standard
form.
a)0.03 m
b)9000 g
c)3450 m
d)0.043 A
e)1 300 000 K