Static friction between two bodies and a surface

[Isiudor]

nothing is wrong, at least not from where I'm sitting.

in fact I received back a quiz I had 2 days ago, and got 100(A+ in conventional terms, I guess).

Doc Al has been great help in helping me understand it all.

thanks again.

 

[tigeranishg]

the answer given by ur textbook is correct
u can solve the problem if u know seudo force topic

 

[tigeranishg]

if u want the block A to be stationary with respect to bolck B.
the net force acting on it must be equal to zero.
fmax a,b = 40
a = 40/5=8
now a seudo opp in direction to this frictional force should act to keep it in rest.
so the block B must move with accelaration of 8
on bolck B frictional force 20N is acting back.
F - fmaxa,b = ma
F- 20 = 160
f = 180N
any doubt contact <personal email removed>
i will explain through a diagram