A 3.0-kg cart and a 2.0-kg cart approach each other on a horizontal air track.They collide and stick together.After the collision their total kinetic energy is 40 J.The speed of their center of mass is:
A)0 m/s
B)2.8 m/s
C)4.0 m/s
D)5.2 m/s
E)8.0 m/s

Question

Quizplus · Accepted Answer

The total kinetic energy before the collision is equal to the total kinetic energy after the collision. The speed of the center of mass is the same before and after the collision. The speed of the center of mass is:$$v_{cm}=\frac{p}{m}=\frac{m_1v_1+m_2v_2}{m_1+m_2}=\frac{(3.0	ext{ kg})(0)+(2.0	ext{ kg})(0)}{3.0	ext{ kg}+2.0	ext{ kg}}=0	ext{ m/s}$$

A 30-Kg Cart and a 2