Significant Figures involving constants

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Alma Cruz 1A
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Joined: Fri Jun 23, 2017 11:40 am

Significant Figures involving constants

Postby Alma Cruz 1A » Sun Jul 02, 2017 12:35 pm

When calculating problems involving constants such as the speed of light, do we use the number provided in the solutions manual (c=2.998x10^8) or the one provided in the list of equations and constants (c=2.99792x10^8)?

In other words, how do we know how many significant figures to correctly use and when to round?

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Re: Significant Figures involving constants

Postby Chem_Mod » Sun Jul 02, 2017 1:15 pm

For homework problems use the constants with more significant figures.

Most of the time constants have more significant figures than the measured (given) values in the problem.
Therefore using a constant with 6 sig fig versus 4 sig fig is not that helpful when the calculation involves measured numbers with only 2 sig fig.

As I have typed several times this week:
Everyone is given the same constants and equations in all my tests and exams. Therefore in a test/exam everyone is using the same information (numbers).

Sheel Shah 1H
Posts: 33
Joined: Fri Sep 29, 2017 7:04 am

Re: Significant Figures involving constants

Postby Sheel Shah 1H » Tue Oct 03, 2017 10:05 pm

I would use the one provided with list of equations, just because it has been measured to increased accuracy, and you may be expected to do the same.

I would also look for what other values in the question have been rounded off to. For example, if all the values in a question have 3 significant figures, use the 3 sig figs in your answer as well :)

- Sheel Shah

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