Based on your understanding of force balances, guess whether a selected member of the truss is under compression, under tension, or is a zero member. Set the diagonal and vertical point loads with sliders. The reaction forces (blue) are calculated and displayed on the truss. Select “guess force on a member”, use the popup menu “select a member” (from 1 to 13), and then select “compression”, “tension” or “zero member” from the next popup menu. Check the “check answer” box to see if your guess is correct. Members under compression are green with arrows pointing outward, members under tension are red with arrows pointing inward, and zero members are black. A zero member is under neither tension nor compression; it has a force of 0 kN. Zero members act as additional support for the structure. Select “solved truss” to see the numerical values of all members.