SI Units


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salvadorramos3k
Posts: 72
Joined: Wed Sep 18, 2019 12:18 am

SI Units

Postby salvadorramos3k » Thu Oct 17, 2019 6:06 pm

So since the wavelength in question 1B.23 is given in pm and we know that the constant for 1 amu is 1.67493x10^-27 kg, does that mean that before we do any calculations we have to convert them to meters and grams? Also, how would the cancellations of the units work for that? I know that velocity is m/s, but then there are J in the equation and I'm not seeing what is going to cancel them out. I know this is a lot, let me know if I have to clarify my question. Thank you so much! :)

Sarah Zhari 1D
Posts: 103
Joined: Sat Sep 14, 2019 12:16 am

Re: SI Units

Postby Sarah Zhari 1D » Thu Oct 17, 2019 6:41 pm

If you are using the equation wavelength=h/p, you need to convert the wavelength to metres, but you do not have to convert the mass of the neutron to grams, and you have to leave this mass in kilograms because the units for momentum(p) is kgm/s

Amanda Lin 2I
Posts: 101
Joined: Sat Aug 17, 2019 12:15 am

Re: SI Units

Postby Amanda Lin 2I » Sat Oct 19, 2019 1:34 pm

The wavelength would need to be in meters, but the mass of the neutron can stay in kg because that is the SI unit for mass.

Also, 1 J = 1 kg*m^2*s^-2, so the units would cancel out leaving you with m/s for your final answer.

Robert Tran 1B
Posts: 118
Joined: Thu Jul 11, 2019 12:15 am

Re: SI Units

Postby Robert Tran 1B » Sat Oct 19, 2019 1:54 pm

Since 1 J = 1 kg*m^2/s^2, this will allow the kg and m to cancel out. Thus, you should convert the pm to m, but you can leave the kg alone so that it cancels out. Just make sure that your units always cancel out to determine whether you need to convert them or not.

Robert Tran 1B
Posts: 118
Joined: Thu Jul 11, 2019 12:15 am

Re: SI Units

Postby Robert Tran 1B » Sat Oct 19, 2019 1:55 pm

Since 1 J = 1 kg*m^2/s^2, this will allow the kg and m to cancel out. Thus, you should convert the pm to m, but you can leave the kg alone so that it cancels out. Just make sure that your units always cancel out to determine whether you need to convert them or not.


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