A realistic view of friction

The force of friction between the floor and a box depends on several factors. We'll spend more time on friction later in this course, but for today's purposes, we can treat it like so:

    force of friction  =  0.1 * (force of box on floor)

So, once again, consider Bob and the box.

Bob is pushing box of mass 80 kg. How hard must he push the box in order to give it an acceleration of 0.2 m/s^2 to the right?

   force        x            y
  --------------------------------
           |          |         
           |          |         
           |          |         
           |          |         
           |          |         
           |          |         
           |          |         
           |          |         
  --------------------------------
   total   |          |
  --------------------------------



                x           y
  --------------------------------
   accel   |          |
           |          |
  --------------------------------