Momentum Practice Test

Two skaters collide elastically: $m_1=50,\text{kg}$ with $v_{1i}=+4.0,\text{m/s}$ and $m_2=70,\text{kg}$ with $v_{2i}=0$. Afterward $v_{2f}=+3.0,\text{m/s}$. What is the final velocity of skater 1?

A stationary $10,\text{kg}$ device explodes into $6.0,\text{kg}$ and $4.0,\text{kg}$ fragments; the $6.0,\text{kg}$ fragment has $-5.0,\text{m/s}$. Determine the velocity of the $4.0,\text{kg}$ fragment after the explosion.