What type of friction is there?

Answer 1

1) Static Friction: When it's hard to move an object (i.e.: moving a large refrigerator box is difficult because of the large mass pressing down and the static friction between the box and the floor)

2) Sliding Friction: Tiny friction particles in between objects that slow them down (i.e.: moving a cafeteria tray in the lunchline--there's a little bit of friction between the tray and the metal bar, which causes the tray to move slowly)

3) Rolling Friction: The friction between wheels (or anything rolling) and the ground. (i.e.: riding a bike. Without rolling friction, we would speed out of control. Walking would also be impossible because our feet collide with the pavement and gently roll off. With no friction, we'd be slipping and sliding everywhere! =D)