1) The final velocity of the two trains is 6 m/s to the right
2) It is an inelastic collision
Explanation:
1)
We can solve this problem by using the law of conservation of momentum: in fact, in absence of external forces, the total momentum of the two trains must be conserved before and after the collision.
Therefore we can write:
where:
is the mass of the first train
is the initial velocity of the first train
is the mass of the second train
is the initial velocity of the second train (initially at rest)
is the final combined velocity of the two trains
Solving the equation for v, we find the final velocity of the two trains:
2)
There are two types of collisions:
- Elastic collision: in an elastic collision, both the total momentum and the total kinetic energy of the system are conserved
- Inelastic collision: in an inelastic collision, only the total momentum is conserved, while the total kinetic energy is not (part of it is converted into thermal energy due to internal frictions)
To verify what type of collision is this, we can compare the total kinetic energy before and after the collision:
Before:
After:
As we can see, the kinetic energy is not conserved, so this is an inelastic collision.
Learn more about momentum here:
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