A car is moving towards North. What will be the direction of force of friction acting on this car due to surface of road ?

Ball bearing is a device which usually converts:

When a pencil cell is released from a certain point on an inclined wooden board, it travels a distance of 35 cm on floor A before it comes to rest. When the same pencil cell is released from the same point on the same inclined board, it travels a distance of 20 cm on floor B before coming to rest. Which floor, A or B, offers greater friction? Give reason for your answer.

You spill a bucket of soapy water on a marble floor accidently. Would it make easier or more difficult for you to walk on the floor? Why?

What kind of friction comes into play:

(a) when a block of wood kept on table moves slowly ?

(b) when a block of wood kept on table just tends to move (or slip)?

(c) when a block of wood kept on cylindrical iron rods moves?