Determining maximum value of the average normal stress

In the problem attached, why are the pins not included in the calculation of area when the links are in tension? But the pins are included in the calculation of area when the links are in compression. See attached file for full problem description.

System Dynamics (state-variable models)

This a question from the topic (System Dynamics). It is from the book (System Dynmaics, William J Palm) The question is attached. It deals with state-variable models.

Drawing the hidden, visible, and center lines on the orthographic views of the attached file.

Draw the hidden, visible, and center lines on the orthographic views of the attached file. Then in the empty space sketch a pictorial of each of the orthographic views. See attached file for full problem description.

Create full or offset sections from the views given

Create full of offset sections from the views given below as indicated by the cutting places. See attached file for full problem description.

Mechanical Engineering Design

I didn't know where to put this exactly like whether in (Engineering Design or , Mechanical Engineering Design (industrial) ). Please see the attached .zip file which has prob.zip (the question), (look at this one first) 1.jpg and 2.jpg