### Momentum

Posted:

**Thu Oct 25, 2018 7:02 pm**When using DeBroglie Equation, will the momentum always be given or would there be circumstances where we have to solve for it, if so how would we go about doing that? Thanks!

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=18&t=34821

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Posted: **Thu Oct 25, 2018 7:02 pm**

When using DeBroglie Equation, will the momentum always be given or would there be circumstances where we have to solve for it, if so how would we go about doing that? Thanks!

Posted: **Thu Oct 25, 2018 8:05 pm**

The mass and the velocity separately and make you multiply it together to be momentum (p = m x v), but other than that I'm sure the momentum will be given most of the time from the problems I did in the homework.

Posted: **Thu Oct 25, 2018 8:20 pm**

The momentum might not be given, for instance the question could give you the wavelength and ask you to solve for the momentum using the DeBroglie Equation where momentum is p=h/lambda. So you know lambda (the wavelength) and h is a constant given to you, so therefore you can solve for the momentum (p).

Posted: **Sat Oct 27, 2018 6:58 pm**

You would have to calculate the mass times the change in velocity to calculate the momentum (p) at times.

Posted: **Fri Nov 02, 2018 9:44 am**

If the momentum is not provided, you can calculate it with p = mv, where m is mass and v is velocity. Since h is in terms of J, don't forget to convert mass to kg and velocity to m/s!

Posted: **Fri Nov 02, 2018 12:10 pm**

If the momentum isn't given, you just solve for momentum with the equation p = mv where m is the mass (kg) and v is the velocity (m/s)

Posted: **Sat Nov 03, 2018 4:04 pm**

you can be given just mass and velocity and you would have to solve it yourself

Posted: **Sat Nov 03, 2018 9:52 pm**

I would recommend using a systematic approach to these kinds of problems. Just write the equation that you need to use to find the answer and if you donâ€™t have all relevant information for that equation them most likely you would have to use another equation like de Broglie to get that information and finish solving it. It is possible that they wont give you ALL the information directly for a given equation.

Posted: **Sun Dec 09, 2018 10:47 am**

You will not always be given the momentum. Solve the debroglie equation algebraically. The question will always give you enough variables to solve for the missing ones.

Posted: **Sun Dec 09, 2018 2:06 pm**

You most likely wont be given momentum, but one of the two parts making up momentum, either m or v.

Posted: **Sun Dec 09, 2018 7:06 pm**

For momentum, either velocity or mass will usually be given. A question might ask you to solve for a missing variable.