sorry accidentally posted here.
First one I believe but im not completely sure
Answer:
For the first situation, we first need to find the mass of the second train car.
In order to do that, we apply the conservation of the amount of movement:

and we have as a result:
m2 = 289.6875
For the second situation, also we will apply the conservation of the amount of movement:

and we have as a result:
V = 2.64 (it is moving to the right)
Answer:
Social media has helped many businesses grow and promote itself, and has helped people find a better way to connect and communicate with one another. On the other hand, it's also provided many people with problems involving mental health, emotional insecurities, and waste of time
Explanation:
what they said is correct
Answer:
5.7141 m
Explanation:
Here the potential and kinetic energy will balance each other

This is the initial velocity of the system and the final velocity is 0
t = Time taken = 0.04 seconds
F = Force = 18000 N
a = Acceleration
g = Acceleration due to gravity = 9.81 m/s²
Equation of motion

From Newton's second law

Squarring both sides

The height from which the student fell is 5.7141 m