## College Physics (4th Edition)

After the collision, the velocity of the helium atom is $266~m/s$ to the right.
We can use conservation of momentum to find the helium atom's velocity after the collision: $m_h~v_{h2}+m_o~v_{o2} = m_h~v_{h1}+m_o~v_{o1}$ $m_h~v_{h2} = m_h~v_{h1}+m_o~v_{o1}-m_o~v_{o2}$ $v_{h2} = \frac{m_h~v_{h1}+m_o~v_{o1}-m_o~v_{o2}}{m_h}$ $v_{h2} = \frac{(4.00~u)(618~m/s)+(32.0~u)(412~m/s)-(32.0~u)(456~m/s)}{4.00~u}$ $v_{h2} = 266~m/s$ After the collision, the velocity of the helium atom is $266~m/s$ to the right.