# how do we decide the nature of friction in a system of two blocks not under isolation?

Anantha Krishnan
18 Points
9 years ago

If the two blocks are not moving relative to each other then its static friction and vice versa then its kinetic friction.

rupali sehgal
19 Points
9 years ago

what if a force is acted upon one of the blocks and the direction of the impending motion of the other is not know?

James Macmillan
20 Points
9 years ago

Suppose the force is acted upon the lower box, then the lower box will move forward with respect to the upper box therefore the lower box will face two types of frictional force one from the ground and the other from the lower surface of the upper box as the lower box is moving with respect to the upper box

Now for the upper box, Upper box will move backward with respect to the lower box therefore friction will acts forward. Remember direction of friction depends upon relative motion

If they move with a common acceleration (wrt ground)  then it is static friction and if they move with different acceleration (wrt ground) then it is kinetic friction