A simple quick return mechanism is shown in the figure. The forward to return ratio of the quick return mechanism is 2 : 1. If the radius of the crank O₁ P is 125mm, then the distance 'd' (in mm) between the crank centre to lever pivot centre point should be

Match the approaches given below to perform stated kinematics/dynamics analysis of machine

Analysis
$$P.$$ Continuous relative rotation
$$Q.$$ Velocity and acceleration
$$R.$$ Mobility
$$S.$$ Dynamic - static analysis

Approach
$$1.$$ D' Alembert's principal
$$2.$$ Grubler's criterion
$$3.$$ Grashoff's law
$$4.$$ Kennedy's theorem

An epicyclic gear train is shown schematically in the adjacent figure The sun gear 2 on the input shaft is a 20 teeth external gear. The planet gear 3 is a 40 teeth external gear. The ring gear 5 is a 100 teeth internal gear. The ring gear 5 is fixed and the gear 2 is rotating at 60 rpm CCW (CCW $$=$$ counter-clockwise and CW $$=$$ clockwise)

The arm 4 attached to the output shaft will rotate at

The rotor shaft of a large electric motor supported between short bearings at both the ends shows a deflection of $$1.8$$ mm in the middle of the rotor. Assuming the rotor to be perfectly balanced and supported at knife edges at both the ends, the likely critical speed (in rpm) of the shaft is