They would fall with the same acceleration
Of the materials listed wood is the best insulator. It would be the least hot if exposed to similar temperatures.
To solve the problem it is necessary to apply the concepts related to Force of Friction and Tension between the two bodies.
In this way,
The total mass of the cars would be,


Therefore the friction force at 29Km / h would be,




In this way the tension exerts between first car and locomotive is,



Therefore the tension in the coupling between the car and the locomotive is 
To solve the problem it is necessary to use the concepts related to the calculation of periods by means of a spring constant.
We know that by Hooke's law

Where,
k = Spring constant
x = Displacement
Re-arrange to find k,




Perioricity in an elastic body is defined by

Where,
m = Mass
k = Spring constant


Therefore the period of the oscillations is 0.685s
Answer:
a)At the mean position
b)At the extremes positions
Explanation:
Given that mass is having oscillation motion.
We know that
1. At the mean position -The velocity of the mass is maximum and the acceleration of the mass is minimum.The net force on the mass will be zero.
2. At the extreme position-The velocity of the mass is minimum and the acceleration of the mass is maximum.The net force on the mass will not be zero.
Therefore
a)At the mean position
b)At the extremes positions