Set-Up For Equations Notes

The first two steps are identical to Dimensional Analysis Notes

1. Write down unknown (units and in more complex problems what substance)

2. Write down all known units including conversion factors

• A conversion factor is anything that allows you to go from one unit to another unit(s). For example, density it is a conversion factor between mass (g) and volume (cm³).
  
• When you are determining which information to change units, you always change the single unit information to the units of an multiple unit information.
• You will need to do Dimensional Analysis (DA) to some of the known information so that when you plug into equation units will cancel correctly.
• When you are changing the units using DA here, the number of sig fig in the changed number will be the same as the original number.

• a. Write the original equation down.
• b. Manipulate the equation using the variable so that you have new equation where the desired variable is alone one side of the equal sign and all other variables are on the opposite side of the equal sign
  • You can not write over the original equation
  • You can not show any work to get the manipulated equation, just simply write the manipulated equation on the next line down from the original equation
• c. Then plug the number/units into the manipulate equation.

• For some manipulated equations, you will get the number with a unit that needs to be converted into another unit. So at this point you are keeping 1 more sig fig than in answer. You do Dimensional Analysis to get to desired units.
• Remember:
  
  • Number must be in scientific notation if greater than 1E3 or less than 1E-3
  • One number before answer in N+1 (one more sig fig as in answer), correct SN and units
  • Answer in correct SN, SF and units