I was riding my bicycle downhill. When the street leveled I realized I had forgotten something so I started turning around without pedaling, pretty much using the momentum I had acquired. Soon I was moving in the complete opposite direction, still without having to pedal.
I couldn't help but thinking how that was possible.
I understand the momentum has a direction arrow and somehow I changed that arrow to the opposite direction. Of course I was going much slower by the time I completely turned around, but still moving.
Is the friction of the wheel against the floor somehow like tiny collisions that "bounce" that momentum force gradually changing that direction? (To the expense of losing energy quicker, thus, speed)?
I used the bike example only because that's when the doubt popped up, but the same I can ask about a ball rolling down and going through a loop or a skier going down a hill and jumping up in a 90 degrees (relative to the downhill part) ramp
What's the physics and maths behind the momentum change to the opposite or perpendicular direction of a moving object when no extra force is applied?