Hukum Newton II

(A)   Percepatan benda

\begin{equation*}
\begin{split}
\Sigma F & = m \:.\: a \\\\
F - f & = m \:.\: a \\\\
20 - 4 & = 2 \:.\: a \\\\
16 & = 2 \:.\: a \\\\
a & =4 \text{ m/s}^2
\end{split}
\end{equation*}

(B)   Jarak yang ditempuh benda selama 10 detik

\begin{equation*}
\begin{split}
S & = v_o \:.\: t + \tfrac 12 \:.\: a \:.\: t^2 \\\\
S & = 0 + \tfrac 12 \:.\: 8 \:.\: 10^2 \\\\
S & = 400 \text{ m}
\end{split}
\end{equation*}