Question

(f) A railway wagon of mass 50000 kg moving with a velocity of 3.6kmph baks into another wagon of mass 30000kg that is at rest on a level railway track. After coupling is made, find the velocity of the coupled wagons

Answer 1

In this kind of questions, it is best to apply CONSERVATION OF LINEAR MOMENTUM principle:

• This principle states that the net initial and final momentum will be same , when no external force acts on system.

• Let final velocity be v.

$\rm \therefore P_{i} = P_{f}$

$\rm \implies \: (50000 \times 3.6) + (30000 \times 0) = (50000 + 30000)v$

$\rm \implies \: (50000 \times 3.6) = 80000v$

$\rm \implies \: 80000v = 180000$

$\rm \implies \: v = 2.5 \: m {s}^{ - 1}$

So, after coupling of wagons, velocity will be 2.5 m/s.