MecMovies 4.0 : M5.6: Coaxial Tube and Core

The figure shows the free body diagram of the tube near the free end B. The load on top of the tube is P which equals 30 kilo newtons directed vertically downwards. The reaction force on member 2 is F subscript 2 directed vertically downwards. The reaction force at the base of the tube is F subscript 1 directed vertically downwards.

Begin by drawing a free-body diagram at end $B$ .

The free-body diagram cuts through tube $(1)$ and core $(2)$ . Internal axial forces $F_{1}$ and $F_{2}$ will be assumed to exist in each component. Further, tension forces will be assumed in each, even though intuitively it is expected that the forces will be compression.

We will always assume that internal forces are tension so that we can develop a consistent problem-solving approach for problems of this type.