A column has a rectangular cross-section of 10 mm $$ \times $$ 20 mm and a length of 1 m. The slenderness ratio of the column is close to

A double - parallelogram mechanism is shown in the figure. Note that PQ is a single link. The mobility of the mechanism is

For the four - bar linkage shown in the figure, the angular velocity of link AB is $$1$$ rad/s. The length of link CD is $$1.5$$ times the length of link $$AB$$. In the configuration shown, the angular velocity of link CD in rad/s is

A mass of $$1$$ kg is attached to two identical springs each with stiffness $$k=20kN/m$$ as shown in the figure. Under frictionless condition, the natural frequency of the system in $$Hz$$ is close to