We'll have two sliding blocks and a wall.

我们有两块滑动的方块和一堵墙。

In the free-body  diagram mr.p did before of the sliding block, the force applied and force of kinetic  friction were in the same direction.

在 mr.p 之前做的滑块的自由体图中，施加的力和动摩擦力方向相同。