Let the units work for you!

1. Let the units work for you!

2. Step 1: Write down the unit you need for your answer on the right side of your paper Step 2: Write down the unit you are starting with on the left side of your paper Step 3: Try putting in equivalent units until they all cancel and give you what you want

3. Examples of equivalent units 5280 ft 12 in 60 min mile ft hr 1m 1 min 1 yard 3.3 ft 60 sec 3 ft 55 mi 1 mile 1 yr 88.5 km 1609m 365.25 days

4. Example In our “constant force” experiment we used a weight to pull cars across the floor. We were surprised to see how much they accelerated (changed speed) Some of the cars reached speeds of 150cm/sec That sounds fast, but what is that in mi/hr?

5. mi cm hr sec Step 1- I want an answer in mi/hr, so I will put that on the left Step 2- I have cm/sec so I will put that on the left Step 3- add equivalencies, one at a time until you can convert the units. I usually leave the numbers out untilI determine what units will work

6. sec cm = 1 hr hr cm cm m mi sec x x mi = cm m hr hr x Remember you are trying to change cm/sec into mi/hr

7. 3600 sec 1 hr 150 cm 540000cm sec hr x 540000cm = hr 1mi 1 m x 3.36 mi x = 100 cm hr 1609 m Remember you are trying to change cm/sec into mi/hr