List three reasons a cell may undergo mitosis

-Growth of an organism (cells divide so that a baby grows bigger)
-Repair (to replace damaged cells)
-Replacing older cells that will die in a matter of time

Hope this helps. 

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on