Two objects colliding & sticking together, what is their final speed?

[itsmarasilly]

Homework Statement

Two freight cars, each with a mass of 2.5 multiplied by 10^5 kg, collide and stick together.
One was initially moving at 3.4 m/s and the other was at rest. What is their final speed?

Homework Equations

m(vf-vi)

The Attempt at a Solution

(2.5*10^5)(0-3.4)= -850,000
= -8.5 * 10^5 m/s

 

[vineroon]

The main thing you can use in the problem is conservation of momentum:

m₁v₁+m₂v₂=(m₁+m₂)v'

This equality is a result of the completely inelastic collision. The question asks you to solve for v'.

 

[thomate1]

The final speed of the combined freight cars would be -8.5 * 10^5 m/s. This is because the initial velocity of one of the cars was in the opposite direction of the other car, causing a negative value in the final speed calculation. This negative value indicates that the combined cars are moving in the opposite direction of the initial velocity of the first car, at a speed of 8.5 * 10^5 m/s. This is a basic application of the conservation of momentum principle, where the total momentum of the system remains constant before and after the collision. In this case, the initial momentum of the first car is equal to the final momentum of the combined cars.