\begin{frame}
  \frametitle{Newtons Law of Cooling/Warming}
  
  \begin{block}{Newtons Law of Cooling}
  The rate of cooling of an object is proportional to the
  temperature difference of the object and surrounding temperature.
  \end{block}
  \pause\medskip
  
  Let
  \begin{itemize}
  \pause
    \item $T(t)$ be the temperature after time $t$, and
  \pause
    \item $T_s$ the temperature of the surroundings. 
  \end{itemize}
  \pause\medskip
  
  Then the law can be written as differential equation:
  \begin{talign}
    T'(t) = k(T(t) - T_s)
  \end{talign}
  where $k$ is constant.
  \pause\medskip
  
  This is not yet the form that we need. Let 
  \begin{talign}
    y(t) = T(t) - T_s &&\mpause[1]{then} &&\mpause[1]{y'(t) = T'(t)}
    &&\mpause[2]{thus} &&\mpause[2]{y'(t) = ky(t)}
  \end{talign}
  \pause\pause\pause
  Thus the solution for $y$ is an exponential function $Ce^{kt}$.
\end{frame}