A 0.5kg wooden block is placed on top of a 1.0kg wooden block. The coefficient of static friction between the two blocks is 0.35. The coefficient of kinetic friction between the lower block and the level table is 0.20.
What is the maximum horizontal force that can be applied to the lower block without the upper block slipping?
Fnet = ma
Fk = μkmg
Fs = μsmg
The Attempt at a Solution
I understand that the acceleration of both blocks will have to be the same for the top block to not slip. However, I have problems understanding the free-body diagrams given in the final solution compared to the ones in my attempt at the solution.
These are the free body diagrams given in the final solution:
By Ff max they mean static friction and by Ff they mean kinetic friction
What I do not understand is:
1) Why is the applied force in the system diagram if it is only being applied to the bottom block?
2) Why does the system diagram include only kinetic friction when it is only being applied to the bottom block?
3) Why are the forces the boxes are exerting on one another not included?
In my attempt at solving this question, I drew two free-body diagrams:
As mentioned before, my attempt gave me the wrong answer. Also, through some research, I found solutions to similar questions with free-body diagrams showing the static friction between the two blocks also affecting the bottom block in addition to the kinetic friction (both in the left direction). I'm not sure how that would work.