If there were no static friction between the soles of your shoes and the ground, then you could move your feet back and forth but your body would never go anywhere.
Same for using tires to move a car, a bus, a bicycle or a motorcycle.
2). Sleeping
If there were no static friction between your jammies and the sheet, you would slide right off of the bed whenever there was the slightest breeze of air in the room.
to calcukate average speed it's unimportant what happened on the way, but we need onky to know total distance d total time. so average speed was : 240 km / 4 hours = 60 km/h
