Chapter 7, Problem 8P

To determine

To Find: Mass of the second car.

Explanation of Solution

Given:

Mass of the boxcar, $m_1=9300\text{kg}$

Initial velocity of the boxcar, $u_1=15.0\text{m/s}$

Initial velocity of second boxcar, $u_2=0$

Common final velocity of the two cars, $v=6.0\text{m/s}$

Formula Used:

As per law of conservation of momentum,

  $\begin{array}{l}{m}_1{u}_1+m_2{u}_2=\left(m_1+m_2\right)v\\ m_2=\frac{m_1{u}_1-m_{1}v}{v-u_2}\end{array}$

Here, v is the final velocity, u is the initial velocity, and m is the mass.

Calculations:

Let the mass of the second boxcar be $m_2$ .

  $\begin{array}{l}{m}_2=\frac{m_1{u}_1-m_{1}v}{v-u_2}\\ m_2=\frac{9300\left(15.0-6.0\right)}{6-0}\\ m_2=13950\text{kg}\end{array}$

Conclusion: 

Thus, the mass of the second boxcar is $13950\text{kg}$ .