Question

A 1091-kg van, stopped at a traffic light, is hit directly in the rear by a 725-kg car traveling with a velocity of +2.18 m/s. Assume that the transmission of the van is in neutral, the brakes are not being applied, and the collision is elastic. What is the final velocity of the car?

Answer 1

Elastic collision means that either the momentum either the kinetic energy are conserved. What that tells us?

Answer 2

\begin{cases} m_1v_{1i}+m_2v_{2i} = m_1v_{1f}+m_2v_{2f} \\ v_{1i}-v_{2i} = - (v_{1f} -v{2f}) \end{cases}

m1 = 1091 , m2 = 725, m2vi = 2.18m/s, m1vi = 0.

Good luck!