Question

In a planar truss, the number of members (m), joints (j), and reactions (r) are related by:

• A. $m + r = 2j$
• B. $m + j = 2r$
• C. $m + r = j$
• D. $m + j = r$

Hint:

For planar trusses, remember the equation $m + r = j$ is crucial for ensuring equilibrium between the joints, members, and reactions.

Answer 1

The Correct Option is C

The relationship between the number of members (m), joints (j), and reactions (r) in a planar truss is given by the equation: \[ m + r = j \] This is a fundamental equation used in the analysis of trusses, where:
- $m$ is the number of members,
- $j$ is the number of joints,
- $r$ is the number of reactions.
This equation ensures the equilibrium of the truss, where the number of members and reactions are balanced with the number of joints.
Thus, the correct answer is option (3), $m + r = j$.