Freight cars roll along a horizontal track as shown below th

Freight cars roll along a horizontal track as shown below. the weights of the cars A, B, and C are 130,000 lb, 100,000 lb, and 150,000 lb, respectively. What is the velocity of the train after they have all coupled? What % of energy is lost in the process?

Solution

Before collision:

Total momentum: 130000*2+100000*1-150000*1.5=135000

After collision: (130000+100000+150000)*V = 380000*V

Therefore: V = 135000/380000 miles/hour = .355miles/hour

Before collison: The net kinetic energy is: (1/2)130000*2^2 + (1/2)100000*1^2 + (1/2)150000*1.5^2 = 478750.

After collison: (1/2)380000*.355^2 = 23275

Energy lost: 455475.

Percentage lost: (455475/478750)*100 = 95.14 %