In addition to cars and wheels/tires, there is also internal friction. Internal friction is what allows you to build up an oil wedge in rotating machinery that relies on a wedge of oil to separate the metal shaft and whatever the bearing surface happens to be, or the ball bearings from the inner and outer race. Friction also allows spinning devices to slow to a stop without the use of brakes...which would also not work without friction. Clutches wouldn't work without friction either, which means you couldn't easily release and re-engage the gears in a transmission...and if it's an automatic transmission, it relies on hydraulic friction to develop pressure in the torque converter. So, in a nutshell, friction is sometimes a bad thing when it results in the loss of mechanical efficiency by converting some of the power applied to useless heat. However, it is also a necessary feature when it is the primary reason a piece of equipment operates...and even then, a portion of that energy will be lost as heat. There is therefore no perfect machines or perpetual motion machines, you always lose some amount of energy to friction, but there are lots of things you couldn't do without friction.
Friction is needed for most things to move. Although it causes the tires to wear out, the car will not be able to move if there is no friction. It will just slip off the surface of the road. A man cannot walk if the ground is frictionless. The shoes will not get grip on the ground and the man will slip.
it has something to do with this: in order for an object to move, it must push off against another object. it is there that friction comes into play. i dont really know the rest.
