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{\bf ADVANCED DYNAMICS --- PHY 4241/5227}\\\vspace {2mm} 
{\bf SOLUTIONS -- SET 8}\\%
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\item{(24)} SI Units. For up-to-date information visit the NIST website.
\begin{enumerate}
\item The second [s] is defined, so that the frequency of light between 
      the two hyperfine levels of the ground state of the cesium 
      $^{132}Cs$ atom is exactly 9,192,631,770 cycles per second.
\item The meter [m[ is defined, so that the speed of light in vacuum
      is exactly 299,792,458~[m/s].
\item A one kilogram weight is kept at S\`evres near Paris.
\item $\rm 1~N = 1~kg\cdot m/s^2$.
\item If two very long parallel wires one meter apart carry equal
      currents, the current in each is defined to be one Ampere [A]
      when the force per unit length on each wire is $2\times 10^{-7}\,
      $[N/m].
\item One Coulomb [C] is the charge flowing through a cross-sectional 
      area of a wire in one second when the current in the wire is one 
      Ampere: $\rm C=A\cdot s$.
\item $\mu_0 = 4\pi\times 10^{-7}\ \rm N/A^2$.
\item $\epsilon_0=8.85418782\times 10^{-12}\ \rm C^2/(N\cdot m^2)$.
\end{enumerate}
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