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### Constant for Speed of Light

Posted: Wed Oct 16, 2019 1:44 pm
I am wondering what constant would Lavelle prefer/require us to use throughout our homework problems and next exam when it comes to speed of light because the Solution Manual used 2.998*10^8 m*s^-1 but in my PLF we used 3.0*10^8 m*s^-1. I am aware that each one can you give you a different answer so I want to make sure I am using the correct constant for speed of light.

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 1:45 pm
I would use 2.998*10^8 m*s-1 because it would give you a more exact answer, but maybe ask your TA!

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 1:48 pm
I think 2.998x10^8 is more accurate but definitely ask if your not positive.

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 3:20 pm
Will there be a difference in our calculations if you used 3.0*10^8 verses 2.998*10^8? I would think using sig figs at the end of our answer our account for any difference in the answers.

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 3:26 pm
Lavelle generally uses 3.0 x 10^8 in class so I believe that is fine.

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 3:51 pm
On Lavelle's website there is a link for a pdf with all the constants and equations and the speed of light used in that is 2.99792 × 10^8 m/s so I assume that using 2.998 would be fine

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 4:59 pm
Personally, I have always used 3.0 x 10^8 m/s for the constant c and my answers have been correct, but I would just check the formula sheet that's given on the test next time just to be safe.

### Re: Constant for Speed of Light

Posted: Wed Oct 16, 2019 5:26 pm
Given he provides 2.99792 × 10^8 m/s on the formula sheet pdf, I would use that, although I'm sure he would specify/be fine with either on homework.

### Re: Constant for Speed of Light

Posted: Thu Oct 17, 2019 1:29 am
I would use the more specific value as it will give you a more exact answer.

### Re: Constant for Speed of Light

Posted: Thu Oct 17, 2019 2:18 am
It is best to use 2.99*10^8 as it is more accurate but make sure you ask your TA about it because when using it, you have to be careful about significant figures of the end result.

### Re: Constant for Speed of Light

Posted: Thu Oct 17, 2019 6:59 pm
2.998x10^8 is most accurate, but for some solutions in the manual it uses even more precise numbers. I think for the tests we're given the constants to use though so we should all be fine!

### Re: Constant for Speed of Light

Posted: Sun Oct 20, 2019 11:36 pm
For tests at least, I used the constant given on the front sheet and I got full points for the problem.

### Re: Constant for Speed of Light

Posted: Wed Oct 23, 2019 1:25 am
Both are correct. 2.998*10^8 m/s is more accurate, but I'm sure you can use 3.0*10^8 m/s as well, as it also gives an accurate answer.

### Re: Constant for Speed of Light

Posted: Wed Oct 23, 2019 11:09 am
In the solutions manual, often the value 2.99x10^8 is used, so I think for accuracy purposes, use the 2.99 value on the test.

### Re: Constant for Speed of Light

Posted: Mon Oct 28, 2019 9:00 pm
2.998*10^8 m/s is definitely more accurate, but 3.0*10^8 m/s is also not wrong for sure. If we can use a calculator then using the more accurate one is definitely more recommend.