Question

A 50 kg skater B collides with a 40 kg skater A initially at rest on ice. They move together after the collision at 5.6 m/s find the velocity of the skater B before the collision

Answer 1

$$m_Av_A+m_Bv_B=(m_A+m_B)v_c,$$ $$0+m_Bv_B=(m_A+m_B)v_c$$ $$v_B=\dfrac{(m_A+m_B)v_c}{m_B},$$ $$v_B=\dfrac{(40\ kg+50\ kg)\cdot5.6\ \dfrac{m}{s}}{50\ kg}=10.1\ \dfrac{m}{s}.$$