To evaluate the expression \( km \) for \( k = 5 \) and \( m = 0 \), you substitute the values of \( k \) and \( m \) into the expression:
\[ km = 5 \times 0 \]
Calculating this gives:
\[ km = 0 \]
Thus, the value of the expression \( km \) is \( 0 \).