## Essential University Physics: Volume 1 (3rd Edition)

$v_1=-67 cm/s$
We know that the sum of the momentums must be 0 due to conservation of momentum: $0= m_1v_1+m_2v_2$ $v_1=- \frac{m_2v_2}{m_1}$ $v_1=- \frac{(91 \ mg)(47 cm/s)}{64 mg}$ $v_1=-67 cm/s$