a) It is absolute, so it does not change.
b) Inertial ones.
c) Inside the train the time will slow down relatively to the outside clock. So if one travel at nearly the speed if light for 2 hours on his clock, for outdoor observers it will look like 3 hours.
Answer:
C
Explanation:
b is 55 miles per hour south or 55mph[South]
the important part to understand is that velocity is a vector meaning it also has to have a direction, in this case south. That is why a (2m/s) is not a velocity, however 2m/s is a speed.
Use the impulse-momentum theorem.

Substitute your known values:

Hope this helps!