The phrase "wanted friction" is a bit of a paradox in science. Friction is generally considered an unwanted force that opposes motion. It causes wear and tear, generates heat, and reduces efficiency.

However, there are situations where friction is essential and therefore "wanted":

* Walking and running: Friction between our shoes and the ground allows us to walk and run. Without it, we would just slide around.

* Braking: Friction between brake pads and the wheels allows cars to slow down and stop.

* Gripping: Friction between our hands and objects allows us to grip and hold things.

* Starting and Stopping: Friction between a car's tires and the road allows it to start and stop smoothly.

* Mechanical Advantage: Friction can be used in mechanical systems to create a force multiplier, such as in a screw or wedge.

So, to summarize:

* Unwanted Friction: Friction that opposes motion and causes wear and tear.

* Wanted Friction: Friction that is necessary for a specific function to occur or provides a benefit.

Instead of "wanted friction", it's more common to talk about beneficial friction, necessary friction, or even controlled friction.