Quick Review: SI Units
Prefixes
Imperial Units
Physical Quantity | SI Unit | Imperial Unit |
---|---|---|
length | meters | feet |
mass | kilograms | pounds |
time | s | s |
Imperial Units Don't Have Prefixes
SI Unit with Prefix | Imperial Unit |
---|---|
kilometer | mile |
meter | feet |
centimeter | inch |
Imperial units use a different unit for everything!
Unit Conversion Practice
1 km | 0.621371 miles |
---|
How many miles are in 10 km?
How many miles are in 50 km?
Unit Conversion Practice
How many kilometers are in 10 miles?
How many kilometers are in 50 miles?
1 mile | 1.60934 km |
---|
Looking Up Conversion Factors
Why Doesn't America Use Metric?
Example1: Air Canada Flight 143
A flight on Canadian Airlines ran out of fuel due to a calculation error. The weight of the plan's fuel was measured in pounds instead of kilograms.
1 pound | 0.453592 kg |
---|
This means the plane had less than half the fuel it was supposed to have. Luckily the pilots were able to make an emergency landing.
Example: Space Probe
In 1998 NASA managed to crash a 200 million dollar space probe into the surface of mars, because of a mistake converting from imperial to metric units.
The probe was completely destroyed
Homework Problems
1. In the U.S. milk is sold by the gallon. How many liters of milk are in two gallons? *1 gallon = 3.8 liters.
2. Take your weight in kg and convert it into pounds.
1 kg = 2.2 pounds
3. Take your height in centimeters and convert it into inches. (look up the conversion factor online.)