Is Friction Actually a Force?
We define force as a push or a pull that moves and object in relation to the amount of push or pull.
All other forces are a combination of a push and a pull. A bend is a double push or a double pull on either side of the point where the shape is changed. A twist is either a double push or a double pull but in opposite directions.
Acceleration is the speed or rate of movement in relation to the amount of push or pull used to start the movement.
Deceleration is defined as the slowing down of a moving object. This is always because there is an opposing force pushing against that movement. This opposing force is explained in Newton’s 3rd Law where he says that every action has an equal and opposite reaction. If the opposing force pushes back against the moving object enough the object will lose all movement and come to a stop.When the opposing force rubs against or grips or in some other way decelerates the moving object disproportionately, the energy transfer is quicker and the by-product is heat. We call this opposing forces situation friction and so friction is not a force in its self but an action of opposing forces.
Energy We should know that energy can never be created, only transferred and dissipated. The sun provides all primary energy which is converted in many ways for secondary transfer which can be further transferred until the energy is so spread out that the effects are no longer concentrated enough to be seen or felt. When all the pushes or pulls against an object are the same, we say that the object is still. We sit still on the floor only because the floor pushes back up at the same rate we push down on it so we stay where we are.
Gravity Generally is definedas a pull force towards the centre of an object. All objects have gravity and the field of influence of this gravity depends on the size of the object. This field is also described in magnetic terms but this can be confusing because magnetism usually relates to metals. Gravity strength does not relate to density but to mass. This means that the bigger the object, the bigger the gravitational field. The earth has a gravitational pull measured as 1 G and the Moon has a lesser gravitational pull measured in comparison as .6 G. The Earth is bigger than the Moon.
The Story
This will explain the process to children:
We fire a shell from a canon. We know that the target is far away so we point the barrel of the canon into the air to fire the shell high to cover the distance. We do this because we know that the shell will slow down as it flies through the air and gravity force will pull it down to the ground when it becomes stronger than the push energy that sent the shell going from the canon.
The shell has potential energy created elsewhere and stored in the gunpowder waiting for a spark to create a rapid transfer of energy to the shell when it explodes. The barrel of the canon directs the energy to push the shell along and out of the barrel. The route the shell follows through the air after leaving the barrel is the trajectory. The trajectory can be calculated once we know the distance, the amount of push and the amount of counter push that the air and gravity will create. This is called aiming the shell at the target.
As the shell flies through the air it rubs against and past the molecules in the air. Each molecule pushes against the shell in its small way transferring some of the energy from the shell. This bleeds or dissipates the energy from the shell into the air.
At the same time the other pull force called gravity becomes apparently stronger than the push force from the canon and begins to cause the shell to change direction and start on its journey to the centre of the earth. If the canon push force was not enough and the energy transfer to the air molecules happens too soon then gravity will take over sooner and the shell will fall short of the target. It won’t go to the centre of the earth however but stop on the ground which will be pushing up at the same rate to keep it still. We would say that the shell ran out of energy and fell to the ground.
The friction caused by the opposing pushes of the shell and the air molecules brings it to a halt once the forces are equal and the gravity pull and the ground trap the shell where it cannot drop any further.
When the Shuttle re-enters the atmosphere the opposing forces are so great that heat caused by the friction between the air and the surface of the Shuttle is a very real problem. Special heat absorbing surfaces have to be made to prevent the Shuttle from overheating and blowing up. If the reentry speed was a lot slower then there would be less opposition so quickly and the temperature would be lower indicating less heat.
When you rub your hands together, the opposing forces soak up more energy because the surface are not very smooth and get hot as a result.
So
Friction is the action of opposing forces. Friction is not a force in its own right.
A Wood 2010