a. Some one pushing a book across the table.
b. a car moving and then hitting a wall.
2. The ball is being acted on by fluid friction.
3. An object in motion tends to stay in motion unless acted on by an out side force.
a. Sliding friction as in ice skating.
b. Rolling friction like bowling.
c. fluid friction (air or liquid) like throwing a ball in to the air.
d. Static Friction like friction with in the moving object.
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