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

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 $${Q_2}.$$

At the instant considered, what is the magnitude of the angular velocity of $${O_4}B?$$

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 $${Q_2}.$$

At the same instant, if the component of the force at joint $$A$$ along $$AB$$ is $$30 N,$$ then the magnitude of the joint reaction at $${Q_2}$$.

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?