Metric System of Measurement

(Correctly called "SI")The metric system is a system of measuring. It has three basic units:
m

the meter for length
kg

the kilogram for mass
s

the second for time


Metric and British Units

One of the principal advantages of the Metric System is its use of only one unit (standard of size) for each parameter (thing that is being measured). The metric units are interrelated in such a way that only five fundamental standards are necessary. These fundamental standards are identified with an * in the tables below.


Parameter:
Metric Unit
British Units
time
duration, delay
second *
s
second, minute
hour, day
frequency
hertz
1/s
cycle per second
length
distance, displacement
meter
1/299 792 458 light sec
m
inch, foot, yard
rod, chain, furlong, mile
velocity, speed
rate of change of position
meter per second
m/s
foot per second
mile per hour, knot
acceleration
rate of change of velocity
meter per second squared
m/s2
foot per second squared
mass
quantity of material
kilogram *
kg
ounce, pound, slug, ton
force
push, pull, or weight
newton
kg m/s2
pound-force
impulse
force times time
newton second
kg m/s
pound-force second
momentum
mass times velocity
kilogram meter per second
kg m/s
pound foot per second
work, energy
force times distance
joule (pronounced "jewel")
= one newton meter
kg m2/s2
foot pound-force
power
rate of doing work
watt
= one joule per second
kg m2/s3
foot pound-force per second
horsepower
area
size of a surface
square meter
m2
square foot, square yard
acre, square mile
pressure
force per unit area
pascal
newton per square meter
kg/m s2
pound-force per square inch
volume, capacity
cubic meter (stere)
m3
pint, quart, gallon
cubic foot, cubic yard
density, heaviness
grams per cubic centimeter
g/cm3
pounds per cubic foot
meask2.gif




Definitions of the SI base units

Unit of length
meter
external image historicalbutton.gifThe meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

Unit of mass
kilogram
external image historicalbutton.gifThe kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.

Unit of time
second
external image historicalbutton.gifThe second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.

Converting Metric Units

We know that:
external image Image11337.gif

This suggests that:
  • To convert length from a larger unit into a smaller unit, multiply by the relevant power of 10.
  • To convert length from a smaller unit into a larger unit, divide by the relevant power of 10.
external image Image15290.gif
You should be able to work confidently with metric units to solve problems in daily life.
Teaching measures
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http://www.teachingmeasures.co.uk/menu.html

Now, do the following exercises:
Exercise 1
Exercise 2
Exercise 3
Exercise 4
Exercise 5
Exercise 6
Do the following test:
Test 1
Test 2
Test 3
Test 4


Now, do the following exercises:
Exercise 1
Exercise 2
Exercise 3
Exercise 4
Exercise 5
Exercise 6
Exercise 7
Do the following test
Test 1
Test 2