Determine the value of axial load in the member 'PQ' of the given pin jointed plane frame.

Concept:

The rule for zero member force:

• At a joint, if three members are meeting, two members are collinear (same line), then force in the third member is always zero (if there is no external load at that joint)
• At a joint, if two non-collinear members are meeting with no external load at that joint then forces in both members will be zero.

Calculation:

(i) At joint P, we get member QP to have zero force member as the other 2 members at the joint ie AP and PC are colinear and there is no load at joint P