Monday, September 13, 2010

Conversions and Dimensional Analysis

Monday September 13, 2010

We started off class today by going over the scribe post. We then took our quiz which was on metrics, sig figs, and density. There was an extra credit question on the quiz in which we were supposed to measure a note card and a post-it and read two graduated cylinders. If anyone was not able to finish the question Mrs. Mandarino will allow you to do it tomorrow while she is teaching the rest of the class. After finishing the quiz, we went over the homework which was page 11 from our journals. The homework was about unit conversion & dimensional analysis which was confusing for many of the students. We went over the first 6 questions from the homework and still need to complete the final 6 questions. In the example below we were working with mass, so we had to figure out which units could convert tons into kilograms.

Ex. Convert 0.00534 ton   to   kg
In order to convert tons to kilograms.
  • We had to find the different units that could allow us to convert tons to kilograms.
  • We knew by looking at the conversion chart that there are 2000 lb in every ton.
  • From there we saw that there are 453.6 g in every pound.
  • This allowed us to have this equation
    • 0.00534 ton  x  2000 lb  x   1 kg    
    •                           1 ton       2.205 lb
  • By looking at the equation we were able to see that the tons and pounds canceled out. This left us with only the kilogram as our single unit.
    • 0.00534 ton  x  2000 lb  x    1 kg         
    •                           1 ton       2.205 lb
  • Now all that was left to do was to multiply all the numerators and divide that by the product of the denominators.
    • (0.00534 x 2000 x 1) = 4.8435374
    •         (1 x 2.205)
  • Finally we knew that we had to change the final answer into 3 sig figs, because the initial amount of 0.00534 had 3 sig figs. The final answer was 4.84 kg

*Remember to show all your work in order to receive full credit.

Shivam P.

Worksheet page 12

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