Two-Force Member

F_{A} = - F_{B} collinear with A B

A member with forces at only two points, and no moments applied, must have equal-and-opposite collinear forces along the line joining the points. Links, truss bars, and hydraulic cylinders are typical.

$F_{A}, F_{B}$ (N): End forces

Step-by-step solved example

A 2 m link from (0,0) to (1.2, 1.6) m carries 5 kN compression. Give the support components at (0,0).

Forces at the two pins are collinear with the member axis.

1. Direction
Unit vector along the link = (0.6, 0.8).
2. Compression
The force on the joint at origin is toward the other end: +5(0.6 i + 0.8 j) = 3 i + 4 j kN.
$3, ma t hb f i + 4, ma t hb f j t e x t k N$

Answer: 3 kN x and 4 kN y (compression push on the origin joint)

10 practice questions

0/10 correct

1.Three-force members can carry

2.If a link has a force in the middle it is

3.Hydraulic cylinder (pins at both ends) is modeled as

4.A cable can take

5.Collinear equal-opposite forces produce

6.To prove a member is two-force, check

7.Direction of force in a two-force member is

8.A rigid body with forces at two points not collinear with the points cannot be in

9.Slider of a piston (ideal) transmits

10.Pin-ended column in statics is treated as