) Train cars are coupled together by being bumped into one another. Suppose two loaded train cars are moving toward one another, the first having a mass of 1.50 × 105 kg and a velocity of 0.30 m/s to the right, and the second having a mass of 1.10 × 105 kg and a velocity of 0.12 m/s to the left. What is their final velocity?

Their final velocity is 0.122m/s

Explanation:

Using the law of conservation of momentum which states that the sum of momentum of bodies before collision is equal to the sum of their momentum after collision. The bodies move with a common velocity after collision.

Momentum = mass × velocity

BEFORE COLLISION

momentum of the first train

= 1.5×10^5 × 0.3

= 0.45×10^5kgm/s

Momentum of second train

= 1.1×10^5 × (-0.12) (velocity is negative since the body is moving towards the left)

= -0.132 × 10^5kgm/s

AFTER COLLISION

Momentum of both bodies is given as:

(1.5×10^5+1.1×10^5)V

= 2.6×10^5V

V is their common velocity

According to the law:

0.45×10^5+(-0.132×10^5) =2.6×10^5V

0.45×10^5 - 0.132×10^5 = 2.6×10^5V

0.318×10^5 = 2.6×10^5V

0.318 = 2.6V

V = 0.318/2.6

V = 0.122m/s