The cross-braces (labeled 1 and 2) in the truss are cables that can support only tension and not compression. They slip past each other where they cross; i. e. they are not pinned together there. (a) Please indicate which of the two cross-braces is in tension (the other will be slack, with zero force), and calculate its tension.
(b) Now suppose that the cross-braces are replaced with regular rigid struts that can support both tension and compression. Would the structure now be statically determinate

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.