6.If a set of given forces are such that their free vectors build a closed polygon, then

7.In which of the following trusses, the method of substitution is required for determining the forces in all the members of the truss by graphic statics ?

8.The force polygon representing a set of forces in equilibrium is a

9.The number of funicular polygons which can be drawn to pass through two specified points in the space diagram are

10.A system of copianar forces is in equilibrium when