We cannot escape the truth that we dwell in a world ruled by friction. There’s friction in your automotive engine, there’s friction between your ft and the bottom, and there may even be friction in your relationships—however that is truly a distinct form of friction that I will not get into. No, I’m simply speaking in regards to the frictional power ensuing from two surfaces interacting with one another. We usually consider friction as a foul factor that we need to cut back—however there are additionally many instances the place we’d like it.
What the Heck Is Friction?
I’ll be sincere—friction is fairly difficult. Imagine that I’ve a block of wooden sliding on a desk. In a way, the atoms on the floor of the wooden block are interacting with the floor atoms on the desk. If you need to look at every of those particular person atom-atom interactions, you will be overwhelmed with the numbers. Even a small block that is 1 cm x 1 cm may need as many as 1016 atoms on the floor. No one has time for that many calculations.
But don’t fret. We have a mannequin that works pretty effectively, (even though it’s not perfect). This mannequin says that the frictional power is parallel to the floor and all the time pointing in the wrong way as the movement (or attainable movement) of the 2 surfaces. That is to say, the frictional power pushes in a route to try to stop sliding.
If the 2 surfaces are stationary relative to one another, we name this “static friction.” The most magnitude of the static frictional power depends upon how a lot these two surfaces are pushed collectively (this is the traditional power, N) and the sorts of supplies interplay (wooden vs. metal or no matter) characterised by the coefficient of static friction (μs). We can write this as the next mathematical mannequin.
Yes, that “less than or equal” signal is necessary. Let me present you why it is there with a easy experiment you could try your self. Take a e-book and put it on the desk. Put stress on the e-book horizontally, however not a lot that the e-book slides. If you drew a power diagram, it’d appear to be this.