Question

Two railroad boxcars collide on a horizontal part of track. The first boxcar has a mass of m1 = 60 000 kg and has an initial velocity of v1i = 1.00 m/s (towards the second boxcar). The second boxcar has a mass of m2 = 80 000 kg and is initially at rest. a) What is the speed of the boxcars after the collision occurs, if a locking mechanism connects them as soon as they collide? b) What percentage of the initial kinetic energy remains as kinetic energy after the collision occurs? c) Write the equation that shows conservation of momentum and the equation that shows conservation of kinetic energy for the case that the locking mechanism does not engage and the boxcars are not connected. You do not need to solve the equations.

Answer 1

m₁ = 60000 kg

vⁱ₁ = 1.00 m/s

m₂ = 80000 kg

vⁱ₂ = 0.00 m/s

Conservation of momentum

Conservation of kinetic energy

For part (a) the two boxcars stick together so they have the same final velocity so

part b)

Initial kinetic energy

final kinetic energy

So percentage of initial K.E. =

                                             =

                                             = 56.86 %