The three types of changes are changes in speed, direction, or both.
The slope of a speed-time graph is acceleration.
Instantaneous acceleration is how fast a velocity is changing at a specific moment.
They both are acceleration, but deceleration is a term often used to describe a negative acceleration.
8m/s+[1*10m/s]=18m/s
The 2nd train will be going 2m/s faster than the 1st train after 10 seconds.
It is not accelerating at a constant rate.
25-0/30=8.3m/s^2
30-25/10=0.5m/s^2