## Combining Different Equations

$c=\lambda v$

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Joined: Sat Jul 20, 2019 12:15 am

### Combining Different Equations

When do we know that it is allowed to combine different equations? In class, we often times intermix E=hv, c=λv, E=pv, etc. Why are we allowed to intermix them and when do we know we need to?

JohannaPerezH2F
Posts: 94
Joined: Wed Sep 18, 2019 12:18 am

### Re: Combining Different Equations

We are allowed to combine equations when they are equal to each other. For example x=2 for x+2=? it would be 2+2=4 because we substitute the variable for the known. This also happens for the equation you listed. Hopefully, this is what you are referring to

Andrew Pfeiffer 2E
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Joined: Sat Sep 28, 2019 12:16 am

### Re: Combining Different Equations

You cannot use the (lambda)(v) = (c) equation or the e = (h)(v) equation for electrons, but you can use them for light!

305421980
Posts: 101
Joined: Sat Sep 07, 2019 12:16 am

### Re: Combining Different Equations

I normally know to combine/mix equations when a certain variable is missing but I know of another equation where the same variable exists and the equation can be rearranged. This often helps in problem solving when I am stuck. I look at the equation sheet and try to fond common variables based on what I need for the problem.

Diana A 2L
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Joined: Sat Aug 17, 2019 12:16 am
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### Re: Combining Different Equations

Also, when showing work, do we have to show the work with the overall equations combined, or can we show our work in more of a step by step process? Here's an example:
Theres E=hv and C=(lambda)v
Here, you can either plug in values individually to derive an answer, or you can combine the equations to obtain something like: E= h(C/lambda).
We can do it either way on the tests and homework and receive credit right?

stephaniekim2K
Posts: 79
Joined: Fri Aug 09, 2019 12:16 am

### Re: Combining Different Equations

Sometimes you are given some info but not others, so in order to solve with the info given you can rearrange them to fit the info you have.

Maya Beal Dis 1D
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### Re: Combining Different Equations

In class I think he mentioned that you can't use electromagnetic radiation equations on electrons. What exactly does this mean?

Ananta3G
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Joined: Wed Sep 18, 2019 12:19 am

### Re: Combining Different Equations

I recommend maybe writing all the equations down at the top of the sheet and then substituting/combining the equations as you see fit.

sarahsalama2E
Posts: 164
Joined: Fri Aug 30, 2019 12:16 am

### Re: Combining Different Equations

Personally, I just write down all the equations i know or see fit and use which ones make sense given the variables that I have in the problem at hand. Make sure that you are using reasonable equations at each step of the problem.