Forces and Motion: Forces and Friction

Forces are pushes or pulls that can change the motion of an object. They can alter the speed, the direction, or the shape of the object.
Frictional force is a force that opposes the motion of an object. It is caused by the interaction between two surfaces attempting to slide past each other.
Friction has beneficial effects such as allowing us to walk without slipping and enabling car tyres to grip the road.
However, it can also be unfavourable. For example, it leads to wear and tear on machinery and other tools, requiring maintenance and repair.
There are different types of friction: static, sliding, rolling, and fluid friction (also known as air or water resistance).
The force of friction depends on the nature of the surfaces involved and how hard they are pushed together.
The contact force is another vital concept, it is created when two objects come into contact with each other.
When forces are balanced, they result in stationary objects, or objects moving at a steady speed in a straight line. When forces are unbalanced, this results in an acceleration (change in speed or direction).
Lubrication reduces friction by creating a thin layer between two surfaces, allowing them to slide more easily over each other.
The resistance of an object to motion, due to friction or any other force, is known as inertia.
Newton’s first law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This is sometimes referred to as the law of inertia.
Newton’s second law establishes a direct proportionality between resultant force and the change in motion, and an inverse proportionality between the mass of an object and the change in motion.
Newton’s third law states that for every action, there is an equal and opposite reaction.
Other forces that can also affect motion include gravitational force, magnetic force, and electrostatic force.
Remember that all objects have a centre of mass - the point at which the weight of the object can be considered to be concentrated.
Work done on an object is defined as the force applied to the object multiplied by the distance the object moves in the direction of the force - work done = force x distance.
Knowledge of forces, friction and associated principles is fundamental in understanding more complex topics in Physics, such as energy transfer, momentum, electricity, and thermodynamics.