Pushing a broke down car, even done by more than one person, is difficult especially if the distance to be covered is quite far. A car is heavy and it requires a lot of force to start the car moving. This is because the inertia of the car to remain at rest is great. Additionally, the force applied in pushing the car must be greater than the frictional force to cause it to accelerate. The frictional force is dependent on the mass of the object which means that the frictional force acting on the car is also great. Finally, with every push of the car, the frictional force will always be present and acting on the opposite direction. The push that will be supplied must be sustained all throughout.
The friends have to combine their forces to be greater than the force of the car pushing back on them (3rd law). The car will remain at rest until an outside force acts on it that it is greater than its own (1st). The speed in which the car is being moved is directly related to the amount of force and direction of the kids pushing the car (2nd).
