Fake Party Scene

The Physics Behind The Fake Party Scene: Home Alone 1
In case you've forgotten the scene...

Physics concepts shown include...
1. Newton's second law when Kevin mans the movements of the doll people

2. Friction occurrence between the steel of the train on the steel of the train tracks


What we can assume/know is how... 
1. When Kevin pulls on the strings that control the movements of the doll people, we can see Newton's second law at work since the doll people move at different accelerations repeatedly in the same direction/cycles, where Newton's second law states that when Fnet does not equal to 0, the object in question will undergo acceleration (a and Fnet are in the same direction). We can assume that on one string, Kevin is pulling a 0.5kg object with a force of 8 Newtons (E), while also experiencing a frictional force of 3.5 Newtons (W).

2. The coefficient of kinetic friction of dry steel on dry steel (aka the train on the train tracks) is 0.42, the mass of the toy train + the attached cardboard cutout is 2kg, and that the normal force acting is = Fg: Fg = mg
            = (2)(9.8)
            = 19.6N


What we can then determine is...
1. The acceleration of the movement of the doll person:
Fnet = Fa + Ff
        = (8) + (3.5)
        = 4.5N (E)

Fnet = ma
4.5/0.5 = 0.5a/0.5
     9 = a
  ∴ a = 9m/s^2 (E)

2. The value of frictional force of the dry toy train's steel wheels on the dry steel train tracks:
Ff = MnFn
    = (19.6)(0.42)
∴ Ff = 8.232N