What are some examples of when you want friction?

Answer 1

Friction is actually a super useful force that we need everywhere. Here are just a few examples. First of all, you want friction when trying to move any distance. Whether it's walking (friction of feet to ground), driving (tires and ground) or even swimming/flying, friction is just vital. On the flip side, you definitely want friction while you are already moving. Every braking system relies on friction to work. If you are in a moving car, you hope that there is friction between the brake pads and brake disks.

There are also less obvious benefits of friction. Friction can be used as a helpful force. For example, lifting a box 5 meters and pushing it up a frictionless ramp to a height of 5 meters would require the same amount of work. Yet in real life, it's easier to push things up ramps. Although the ramp itself has friction, there is usually a greater force of friction between your feet and the ground which actually reduces the amount of work you have to enact onto the box yourself. This concept is useful in many different ways.

If you just look around for man-made inventions, you will find hundreds of other examples. So many different things, ranging from pencils to CPU fans benefit from some form of friction in one way or another