three blocks A B and C are kept one on the other what will be the acceleration of the three blocks if the horizontal force of 10 Newton is applied to block B?
Answers
See, friction is actually a resolution of contact force parallel to the surface . Contact force is always self adjustable( if it's within max limit) , so the lower blocks have tendency to move relative to each other when uppermost block has some force applied on it ( draw fbd u will understand better) .Now to oppose the relative motion between two lower blocks , static friction acts between their surface and hence they move together without slipping . Thus they accelerate at same rate .
However note that this no slipping condition will be there only if external force applied at top most block is such that max limit of static friction is not crossed . If it happens there will be relative motion between blocks and different acceleration is possible .