\(\text{momentum of a given system (excluding friction) is constant, so just pick any time and compute it}\\ \text{we'll pick a time prior to the collision}\\ p = (5~kg)(25~m/s)\hat{i} + (1~kg)(0~m/s) = 125\hat{i}~\dfrac{kg \cdot m}{s}\)
\(\text{momentum of a given system (excluding friction) is constant, so just pick any time and compute it}\\ \text{we'll pick a time prior to the collision}\\ p = (5~kg)(25~m/s)\hat{i} + (1~kg)(0~m/s) = 125\hat{i}~\dfrac{kg \cdot m}{s}\)