Zero Force Members

Use the interactive Figure to determine the zero force members in the truss

Use the Figure below to answer the following questions.

For which angle α of force P_a does member AB become a zero force member?

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For which angle α of force P_a does member AG become a zero force member?

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For which angle δ of force P_d, measured clockwise from the horizontal, does member DE become a zero force member?

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For which angle δ of force P_d, measured clockwise from the horizontal, does member DC become a zero force member?

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Why is member EC always a zero force member?

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A
Because there is no external force acting on the joint
B
Because there is no support reaction at that joint
C
Because it is longer than the other members at the joint
D
Because it is the third member of a joint where the other two members are collinear

When no external forces act on joint A, members AB and AG are zero force members because?

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What following condition is required for member EF to be a zero force member?

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Which of the following conditions are required for a member to be a zero force member by simple visual inspection? Select all that apply.

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A
When two non-collinear members form a joint, and no external load or support reaction is applied, both members are zero force members
B
When two non-collinear members form a joint, and an external load or support reaction is applied, both members are zero force members
C
When three members form a joint, and two are collinear, the third is a zero force member as long as no external force or support reaction has a component along that member
D
When three members form a joint, and two are collinear, the third is a zero force member if an external force or support reaction has a component along that member
E
When four members form a joint, and two are collinear, the other members are zero force members as long as no external forces or support reactions act along either member