3. S.I. / METRIC SYSTEM
Based on the decimal
Power of ten
Most of the world uses
this kind of measuring
system
IMPERIAL / ENGLISH
SYSTEM
Used in the United
States
4.
5. SI Units
• International System of Units (from
French, 1960)
• For high and least values it uses prefixes.
• It is more convenient to use than English
units.
Example:
1kg = 1000g
1m = 1000mm
1kPa = 1000Pa
Units are:
Length – meters (m)
Mass –gram (g)
Force – Newton (N)
Pressure – Pascals (Pa)
Temperature – Kelvin (K) and degree Celsius (°C)
Note:
We can also use
“Scientific Notation”
6. US Customary Units
• Imperial Units / English units (from England, middle ages)
• For high and least values do not use prefixes.
Example:
1 kips = 1000 lb
1 ton = 2000lb = 2 kips
1 ksi = 1000 psi
• It is more challenging to use than SI.
1ft = 12 inches
1mile = 5280 ft.
The units are:
Length – feet (ft) and inches (in)
Mass – Slugs, pound mass (lbm), ounces (oz) and Tons
Force – pound force (lbf)
Pressure – Pound per square inch (psi) and Pound per
square foot (psf)
Temperature – Rankine (R) and degree Fahrenheit (°F)
7. length
1 cm 10 mm
1 m 100 cm
1 km 1000 m
1 in 2.54 cm
1 ft. 12 in
1 m 3.28 ft
1 mile 1.609 km
Mass
1 g 1000mg
1 kg 1000 g
1 T 1000 kg
1 kg 2.21 lbs.
1 slug 14.59 kg
8. CONVERSION OF UNITS
Unit conversion is a process with multiple steps that involves multiplication
or division by a numerical factor or, particularly a conversion factor.
Conversion is the process of changing the value of one form to another for
example inches to millimeters, or liters to gallons.
If we have a given the following:
LENGTH: 1 foot (ft) = 0.3048 meters (m)
MASS : 1 kilogram (kg) = 2.2 pounds (lbₘ)
GRAVITY: 9.8066 m/s² and 32.174 ft/s²
Let us convert the following:
1 mile (mi) to kilometers (km)
1 Newton (N) to Pound (lbf)
1 slug to kilogram (kg)
9. CONVERSION OF UNITS
Unit conversion is a process with multiple steps that involves multiplication
or division by a numerical factor or, particularly a conversion factor.
Conversion is the process of changing the value of one form to another for
example inches to millimeters, or liters to gallons.
PRESSURE:
1 atm
101,325 Pascals (Pa)
14.7 Pound per square inches (psi)
2116.8 Pound per square feet (psf)
CONVERT:
14Pa to psi
10. CONVERSION OF UNITS
Unit conversion is a process with multiple steps that involves multiplication
or division by a numerical factor or, particularly a conversion factor.
Conversion is the process of changing the value of one form to another for
example inches to millimeters, or liters to gallons.
AREA
In conversion of SI units to English Units always remember that the Area is
always squared or raise to power of 2.
CONVERT:
1m² convert it to ft²
300mm² convert it to in²
12. PRACTICE PROBLEMS
1)Convert pound per square feet to Pascals at atmospheric pressure.
2)A circle measures a diameter of 5ft. What is the measurement of its area in
terms of metric system?
3)If an aircraft is traveling at a speed of 250 miles per hour (mph). What is the
speed in meter per second?
4)Find the cross-sectional area of a box in Imperial Units if the length and
width is 5m and 3m respectively.
5)A boy exerted a 45lb force in a ball and with an acceleration of 10m/s2 find
the mass of the ball in metric. the product of mass and acceleration.
6)Convert 1925.5psf to psi and Pa respectively.
7)A circular tube has a cross sectional area of 500mm² , find its diameter in
inches (in).
8)Find the side of a square plate in centimeters, if its area is 144ft²
9)A cylinder has an inner diameter of 3in and outside diameter of 5in. Find the
cross-sectional area. Note: Cross sectional area is difference of the area of
outside and inside diameter.
10)A 150 square meter rectangular lot, has a width of 3 times of its length.
Find the length and width of the lot.
