FRICTION

It’s kind of an understatement to say we encounter friction every day. Friction is the reason we can even move or hold items and… live.

What is friction?

Friction in physics is a resisting force which interacts with an object moving through a medium or across a surface. It is that resistance you feel, pushing back, when you are trying to use a rubber eraser, or trying to slide across a rough surface.

What causes friction?

Friction is associated with motion: most moving objects must encounter friction. It is caused by tiny irregularities between the surfaces in contact.

Most objects are not perfectly smooth so this tiny irregularities undergo a lot of intermolecular interactions some are: cohesion (if similar materials are in contact) and adhesion (if dissimilar materials are in contact). Friction also occurs if the irregularities between surfaces in contact interlock which requires more force needed to break this lock hence moving the object.

Forms of friction

There are two forms of friction: the static and kinetic friction. Static friction is the frictional force which is needed to be overcome before the object begins motion. And kinetic friction is the frictional force acting on a moving object, slowing it down. This is the external force acting on the object to bring it to a halt. So, no matter how hard you kick a ball… it will always stop (Newton’s first law of motion)

RULES OF FRICTION

Friction obeys some discovered rules:

Firstly, friction is independent of the surface area of contact between the surfaces. So regardless of which area of contact between two bricks of equal mass, one stood with the length at the bottom, and one with the length upright dragged on a surface. The friction in both bricks are the same.

Secondly, kinetic friction is independent on velocity. The same force is required to erase a mistake with a rubber eraser, regardless of its speed. Although this is only an approximation.

Thirdly, kinetic friction on a horizontal surface is proportional to the weight of the moving object. When a surface isn’t horizontal, kinetic friction is proportional to the perpendicular, or normal, force applied to the surface by the object.

Finally, friction depends on the nature of the surfaces in contact. As you’ll probably know, sand paper offers more friction to polished glass.

Economic importance

Friction causes a lot of work for people. It wears out the sole of our shoes and our tires.

And since friction is associated with movement most machines and tools specifically those that are meant to move, such as bikes, cars erasers, fans will all wear out someday. Some rather quickly, like, most people would have changed their tires, fan belts, and shoes when they wore out. It’s also a good reason why perpetual motion machines are viewed as a “joke” , due to the energy “lost” (usually in the form of heat and sound), thanks to friction. A lot of effort is being put forth to reduce this wasted energy, such as the invention the ball bearing and lubricants (such as oil and graphite).

Although friction causes problems to engineers and machine users, it is also almost nearly impossible to live without friction: as we will not be able to walk, hold things, eat, drive, and write without friction.Just imagine if friction went off right now: you’ll immediately slip and fall and keep on sliding to the nearest dip. All the pictures on you wall would fall off as the nails slip out of the holes, the thread on everyone’s clothes will begin to unravel followed by numerous car accidents as cars brakes don’t work. Buildings would collapse. Earthquakes will occur. All these followed by even worse disasters will occur, if not for friction.

Thanks for reading this far, and I hope you’ve learnt a great deal about friction, and our love-hate relationship with it.