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vibration calculation question

Find the reduced mass of HCl and calculate the frequency of vibration in cm-1 the force constant for the bond, k, is 400 Nm-1.

I found the reduced mass of HCl to be 1.63E-27 Kg

and used (1/2*pi*c) * sqrt (k/u) and got 263190.31 which is wrong. Where have I gone wrong?
Reply 1
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BJack
19
Original post by jacksonmeg
x


Did you convert c to cm/s instead of m/s?
Reply 2
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jacksonmeg
OP
11
Original post by BJack
Did you convert c to cm/s instead of m/s?


I put C in cm/s, K in N/cm and the mass in grams

update: got the right answer with C in cm/s and K in N/m and mass in kg -shrug-
(edited 8 years ago)
Reply 3
Avatar for BJack
BJack
19
Original post by jacksonmeg
I put C in cm/s, K in N/cm and the mass in grams

update: got the right answer with C in cm/s and K in N/m and mass in kg -shrug-


Remember that the N is a unit of force and so N.m-1 is actually kg.s-2 and so the force constant doesn't need a centimetre conversion. If in doubt, the safest thing to do is work everything out in standard SI units and just do the multiplication/division factor afterwards.

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