A planar closed kinematic chain is formed with rigid links $$PQ = 2.0 m, QR = 3.0 m, RS = 2.5 m$$ and $$SP = 2.7 m$$ with all revolute joints. The link to be fixed to obtain a double rocker (rocker-rocker) mechanism is

A solid disc of radius $$r$$ rolls without slipping on a horizontal floor with angular velocity $$\omega $$ and angular acceleration $$\alpha $$. The magnitude of the acceleration of the point of contact on the disc is

In the mechanism given below, if the angular velocity of the eccentric circular disc is $$1$$ rad/s, the angular velocity (rad/s) of the follower link for the instant shown in the figure is

Note : $$All$$ $$dimensions$$ $$are$$ $$in$$ $$mm$$

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