A block of mass \(m_1\) slides along a rough horizontal table with kinetic friction coefficient \(\mu_k\) and collides with an initially stationary block of mass \(m_2\). High-speed sensors measure the total linear momentum of the two-block system immediately before contact, \(p_i\), and immediately after contact ceases, \(p_f\), over a finite contact duration \(\Delta t\). The measurements show that the final total linear momentum is measurably less than the initial total linear momentum, such that \(p_f - p_i < 0\). Which of the following provides the correct physical explanation for this observation?