Speed of light


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Emily_Stenzler_2H
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Speed of light

Postby Emily_Stenzler_2H » Tue Oct 20, 2020 9:06 pm

I have been using 3.00*10^8 for the speed of light, but I noticed the textbook uses 2.998*10^8. I was thinking this would be determined based on sig figs but the question I'm looking at in the textbook (example 1A.1) has 2 sig figs for the numbers in the question. How do we know which to use? It sounds like grading may be a bit picky and I know these two values would lead to different answers, even though they vary by a small amount. Please let me know :)

Quinton Sprague 1A
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Re: Speed of light

Postby Quinton Sprague 1A » Tue Oct 20, 2020 9:10 pm

Hello,
The value 2.998 x 10^8 m/s is the most precise so although it is easy to remember 3.0 x 10^8, if the grading is very picky, it is likely best to go with the figure closest to its exact value, that being the 2.998 x 10^8 representation of the speed of light.

Kaley Qin 1F
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Re: Speed of light

Postby Kaley Qin 1F » Tue Oct 20, 2020 10:29 pm

For tests, Lavelle said that for constants, he will give you the exact value he wants you to use so there will be no discrepancies between students.

Lorraine Medina 3E
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Re: Speed of light

Postby Lorraine Medina 3E » Wed Oct 21, 2020 12:03 am

Dr. Lavelle has an equation sheet for the tests, so I would use whatever number is on that sheet for the midterm/final.

Veronica Macias 3K
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Re: Speed of light

Postby Veronica Macias 3K » Thu Oct 22, 2020 12:20 pm

Lorraine Medina 3C wrote:Dr. Lavelle has an equation sheet for the tests, so I would use whatever number is on that sheet for the midterm/final.


Dr. Lavelle has an equation sheet on his website already titled "Constants and Equations." This will probably be the sheet we are given on the midterms and final. The value for c on there is 2.99792 x 10^8 m.s^-1. I have been using the numbers for the constants on this equation sheet for problems and they have been giving me the right answers.

t_rasul2I
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Re: Speed of light

Postby t_rasul2I » Fri Oct 23, 2020 11:12 pm

I think for the midterm, since it is multiple choice, we can use either value to calculate because we should still get a very close answer to the correct answer.

505598869
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Re: Speed of light

Postby 505598869 » Sun Oct 25, 2020 1:02 pm

I would use whatever numbers Dr. Lavelle gives us on his constants/equations sheet.

Anya Holbrook 1E
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Re: Speed of light

Postby Anya Holbrook 1E » Sun Oct 25, 2020 3:15 pm

I've been using 2.998 x 10^8 rather than 3.00 x 10^8, and just rounding my final answer to the correct number of sigfigs, and it seems to have been working so far!

Jessica Hu 3L
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Re: Speed of light

Postby Jessica Hu 3L » Sun Oct 25, 2020 9:46 pm

Regardless of the precise constant you use, the test is multiple choice, therefore your answer should be close enough to one of the options given.

Morgan Gee 3B
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Re: Speed of light

Postby Morgan Gee 3B » Sun Oct 25, 2020 9:50 pm

Because our midterm is going to be multiple choice, it probably does not matter too much how many significant figures you use. However, I personally plan on using as many as possible to be as accurate as possible.

Aria Movassaghi 1A
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Re: Speed of light

Postby Aria Movassaghi 1A » Sun Oct 25, 2020 9:58 pm

In the past I've used 3.00 but now I just use the constants that are on the provided page by Dr. Lavelle. However it should not make a big difference on a multiple choice exam.

Joshua Chung 2D
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Re: Speed of light

Postby Joshua Chung 2D » Sun Oct 25, 2020 10:02 pm

Though 3.0 will probably be fine in most questions, you can round to math the sig figs of the given values just to be safe.

SophiaBarden 2E
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Re: Speed of light

Postby SophiaBarden 2E » Sun Oct 25, 2020 10:17 pm

From friends that have taken Lavelle's classes before; The sig figs matter! Lavelle will give you options that give the same answer but with varying sigfigs to test your knowledge (and rounding ability for some reason lol). So make sure you use the exact values given on the constants and equations sheet, and note the sig figs for those numbers.

Griffin G
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Re: Speed of light

Postby Griffin G » Sun Oct 25, 2020 10:20 pm

For this class, I would use 2.99792 x 10^8 m.s^-1 because that is the value given on the constants and equations worksheet Lavelle sent in an email. However, whatever value you use just depends on how accurate you want to be.

alexandralopez 3F
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Re: Speed of light

Postby alexandralopez 3F » Sun Oct 25, 2020 10:21 pm

I would probably go off of the equations sheet Lavelle wants us to use! Its on ccle if you still need it!

Lizbeth Garcia 1F
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Re: Speed of light

Postby Lizbeth Garcia 1F » Sun Oct 25, 2020 10:34 pm

I agree with everyone else, use the one that lavelle will provide on the equation sheet.

Thomas Gimeno
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Re: Speed of light

Postby Thomas Gimeno » Sun Oct 25, 2020 11:32 pm

I wouldn't worry too much because usually the answer accounts for a slight bit of variation based on constants but i think if the text book is using 2.998*10^8 then it's probably your best bet.

Marco Vivar 3G
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Re: Speed of light

Postby Marco Vivar 3G » Sun Oct 25, 2020 11:56 pm

Use the equation sheet. The eq sheet has it listed as c=2.99792*10^8 m/s

Susanna Givan 2B
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Re: Speed of light

Postby Susanna Givan 2B » Sun Oct 25, 2020 11:58 pm

Is c a constant?

Alexa Pham 1D
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Re: Speed of light

Postby Alexa Pham 1D » Mon Oct 26, 2020 11:14 am

Susanna Givan 1L wrote:Is c a constant?


Yes, c is a constant for the speed of light (3.0 x 10^8 m/s)

Keeryth Sandhu 1H
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Re: Speed of light

Postby Keeryth Sandhu 1H » Mon Oct 26, 2020 4:01 pm

It's probably the safest just to use the constant on our formula sheet.

Nandhini Ekambaram 1L
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Re: Speed of light

Postby Nandhini Ekambaram 1L » Mon Oct 26, 2020 5:07 pm

For most problems using 3.0 x 10^8 m/s resulted in the correct answer. But for exams, it would be safer to go with the more precise value given on the formula sheet.

Yolanda_Xing_3A
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Re: Speed of light

Postby Yolanda_Xing_3A » Sun Nov 01, 2020 11:00 pm

I don’t think using either numbers would change the your answer since tests are in MC. Or else, staying with the equation sheet is no wrong.

Andy Hernandez
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Re: Speed of light

Postby Andy Hernandez » Sun Nov 01, 2020 11:05 pm

2.998*10^8

Jacob Schwarz-Discussion 3I
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Re: Speed of light

Postby Jacob Schwarz-Discussion 3I » Sun Nov 01, 2020 11:12 pm

Lavelle is okay with 3*10^8! You don't need to worry about 2.999 he wants us to stick with 3 (:

Jacob Schwarz-Discussion 3I
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Joined: Wed Sep 30, 2020 10:01 pm

Re: Speed of light

Postby Jacob Schwarz-Discussion 3I » Sun Nov 01, 2020 11:12 pm

Lavelle is okay with 3*10^8! You don't need to worry about 2.999 he wants us to stick with 3 (:


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