Question

Four railroad cars, all with the same mass of 11300 kg, sit on a track, as shown in the figure below. A fifth car of identical mass approaches them with a velocity of 19.3 m/s (to the right). This car collides and couples with the other cars.


(a) What is the kinetic energy of car 5 before the collision?

(b) What is the kinetic energy of all five cars just after the collision?

(c) Is the energy conserved in this collision?

1. No
2. Insufficient information
3. Yes

Answer 1

a. KE = 0.5m*V^2
KE = 0.5*11300*19.3^2 = 2,104,569 J.

b. Momentum = 5 * m*V = m1*V1
5 * 11,300*V = 11,300*19.3
56,500V = 218,090
V = 3.86 m/s.

KE = 0.5*5m*V^2
KE = 0.5*5*11,300*3.86^2 = 420,914 J.