Answer:
-1.09m/sec^2
Explanation:
Acceleration= (Vf-Vi)/Time
=12-54.8
= -42.8
= -42.8/39
=-1.09
-ve sign is due to recoil of train
as it suddenly hits brakes.
Answer:
2.73414 seconds
467622.66798 J
Explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
g = Acceleration due to gravity = 9.81 m/s² = a



or

The time taken is 2.73414 seconds
The potential energy is given by

The change in potential energy is 467622.66798 J
Acceleration means speeding up, slowing down, or changing direction. The graph doesn't show anything about direction, so we just have to examine it for speeding up or slowing down ... any change of speed.
The y-axis of this graph IS speed. So the height of a point on the line is speed. If the line is going up or down, then speed is changing.
Sections a, c, and d are all going up or down. Section b is the only one where speed is not changing. So we can't be sure about b, because we don't know if the track may be curving ... the graph can't tell us that. But a, c, and d are DEFINITELY showing acceleration.
There are usually multiple methods for organizing items and information in a scientific investigation.