# Homework Help: Inelastic Collision Scenario Question

1. Sep 12, 2014

### IronManTable

1. The problem statement, all variables and given/known data

A railway carriage with a mass m = 2.45×104 kg is initially travelling to the left with a speed Vi = 3.33 m/s. It collides and couples with (get stuck to) two identical railway carriages move to the left with a speed of Ui = 1.69 m/s.

1. What is the speed of the railway carriage after the collision? (give a negative answer if the speed is to the right.)

2. How much kinetic energy is lost in this collision?

2. Relevant equations

P = m1v1 + m2v2

KE = 1/2mv2

KE (before collision) = 1/2m1v12 + 1/2m2v22

KE (after collision) = 1/2(m1+ m2)vf2

3. The attempt at a solution

1. P = (2.45×104 x 3.33) + 2(2.45×104 x 1.69)
= 1.6x105 kgms-1

∴ P = 1.6x105 = (m1 + 2m2)vf = 7.35x104vf
vf = (1.6x105) / (7.35x104)
vf = 2.18 m/s

2.
KE (before collision) = 1/2m1v12 + 1/2m2v22
KE (before collision) = 1/2(2.45×104 x (3.33)2) + 1/2(2(2.45×104 x (1.69)2)
= 2.06x105 J

KE (after collision) = 1/2(m1+ m2)vf2
KE (after collision) = 1/2( 2.45×104+ 2(2.45×104) ) x (2.18)2
= 1.75x105 J

KE lost = 3.1x104 J

Thank you for any help :)

2. Sep 12, 2014

### HallsofIvy

That's what I get.

3. Sep 12, 2014

### IronManTable

So I assume my working out and answers are correct?