An instantaneous configuration of a four-bar mechanism, whose plane is horizontal, is shown in the figure below. At this instant, the angular velocity and angular acceleration of link $${Q_2}\,\,A$$ are $$\omega = 8\,\,rad/s$$ and $$\alpha = 0$$, respectively, and the driving torque $$(T)$$ is zero. The link $${Q_2}\,\,A$$ is balanced so that its center of mass falls at $${Q_2}.$$

Which kind of $$4$$-bar mechanism is $${Q_2}AB{O_4}?$$

The number of degrees of freedom of a planar linkage with 8 links and 9 simple revolute joints is

In a spring-mass system, the mass is 0.1 kg and the stiffness of the spring is 1 kN/m. By introducing a damper, the frequency of oscillation is found to be 90% of the original value. What is the damping coefficient of the damper?

There are four samples P, Q, R and S, with natural frequencies 64, 96, 128 and 256 Hz, respectively. There are mounted on test setups for conducting vibration experiments. If a loud pure not of frequency 144Hz is produced by some instrument, which of the samples will show the most perceptible induced vibration?