UNITS AND CONVERSIONS

Units of measurement Units are incredibly important in the study of physics! Example: The spider was 4 long. Was it… 4 millimeters? 4 inches? 4 kilometers?

Standard units SI Units (emphasized by our book) “Le Systeme International d’Unites” Length – meter (m) Mass – kilogram (kg) Time – second (s)

METHOD FOR CONVERTING UNITS Draw the box/grid. Write the known quantity (with units) in the top left corner. Put a 1 in the bottom left corner. Write the conversion factor to the right (with units). Put the part with the units matching the known quantity in the bottom, so that the units will divide out. Cancel the units. Are the units left what you are looking for? If not, repeat step 3 and 4 with another conversion factor, again placing the parts so that units will divide out. Multiply across the top and bottom separately. Divide the numbers and write your answer with units. Example: If 1 thingy = 3 whatsits and 9 whatsits = 12 doohickeys, then 100 doohickeys = ___ thingies?

Practice If 5 giants = 38 orcs, then 95 giants = ___ orcs? If 40 diamonds = 520 gold bars and 1 pearl = 130 gold bars, then 20 pearls = _____ diamonds?

ENGLISH -> ENGLISH Same steps as previous conversions. Must memorize conversion factors! Examples: Convert 4 yards to inches. Convert 15 ounces to pounds. Convert 15 fluid ounces to cups. Convert 3 years to seconds.

Metric -> metric Same process, time will be exactly the same. Must know the prefixes! Works the same for length (m), mass (g), and volume (L) Examples: Convert 145 cm to meters. Convert 2.3 kg to milligrams. Convert 78.3 dL to hectoliters.

English <-> Metric You will NOT have to memorize these conversion factors! They will be given on any quiz or test. Examples: Convert 35.56 cm to inches. Convert 0.4 km to yards. Convert 912 ounces to kilograms.

Converting Area Area is measured in square units, such as 𝑖𝑛 2 (square inches), 𝑚 2 (square meters), or 𝑚𝑖 2 (square miles). To convert from one square unit to another, you need to either use the conversion factor twice, or square the conversion factor. Example: Convert 288 𝑖𝑛 2 to 𝑓𝑡 2 .

Converting Volume Volume is measured in cubic units, such as 𝑖𝑛 3 (cubic inches), 𝑚 3 (cubic meters), or 𝑐𝑚 3 (cubic centimeters). To convert from one cubic unit to another, you need to either use the conversion factor three times, or cube the conversion factor. Example: Convert 1 𝑘𝑚 3 to 𝑚 3 .

Practice Convert 23 𝑚𝑖 2 to 𝑘𝑚 2 . Convert 2.5 𝑦𝑑 3 to 𝑓𝑡 3 .