Question

A 5,000 kg freight car moving at 2 m/s runs into a 10,000 kg freight car at rest. They couple upon collision and move away as one body at _______.A) 5 m/s.B) 0.66 m/s. C) 0 33 m/s. D) 1 m/s. E) 2 m/s.

Answer 1

Given data,

Mass of the car 1

$m_1=5,000\text{ kg}$

Mass of the car 2

$m_2=10,000\text{ kg}$

In the initial condition, velocity of car 1 is 2 m/s while car 2 is at rest.

Initial momentum of the car.

$P_0_{}=m_1v_1$

Final momentum of the car.

$P_f=(m_1+m_2)v_f$

Applying conservation of momentum.

$m_1v_1=(m_{_1}+m_2)v_f$

Substitute given values.

$\begin{gathered} v_f=\frac{m_1v_1}{m_1+m_2} \\ v_f=\frac{5000\times2_{}_{}}{5000_{}+10,000_{}} \\ v_f=0.66\text{ m/s} \end{gathered}$

Therefore, the correct option is (B).