3NA Science (Physics)Chapter 1Physical Quantities, Units and Measurement

By the end of the lesson, you should be able to

Physical Quantities

A physical property is a quantity that can be measured

Can you name some physical quantities?

                                                                               

Imagine you ask about the age of a person, and the number is a numerical value.

The information conveyed during the conversation will not be very specific or useful.

How old is your little sister, Jon?

She is 12!

12? 12 months? 12 years old?

No NAKED numbers please!!!Do these numbers make sense to you? What do they lack?

45 897.00

67000

0.325 3 x 108

Quantities, Magnitude, Units The weight of a coin is 12 g.

Physical quantity magnitude

unit

All physical quantities are presented with a magnitude and a unit.

Base Quantities and its Unit

mmetrelength

molmoleAmount of substance

Aamperecurrent

ssecondtime

cdcandelaLuminous intensity

Kkelvintemperature

kgkilogrammass

SymbolBase unitBase quantity

Very small and very BIG quantities

Bacteria is very small…..it is about 0.000 001 m long…

The sun is 149 342 000 000 m away from us…

A more efficient way of expressing very big or very small number is to do so in scientific notation, using appropriate prefixes .

Prefixes

giga (G)mega (M)kilo (k)

deci (d)centi (c)milli (m)micro ()nano (n)

X 109

X 106

X 103

X 10-1

X 10-2

X 10-3

X 10-6

X 10-9

X 1 000 000 000X 1 000 000X 1 000

X 0.1X 0.01X 0.001X 0.000 001X 0.000 000 001