The equation of free vibrations of a system is $$\frac{{{{\text{d}}^2}{\text{x}}}}{{{\text{d}}{{\text{t}}^2}}} + 36{\pi ^2}{\text{x}} = 0{\text{,}}$$    its natural frequency is

In considering friction of a V-thread, the virtual coefficient of friction (μ₁) is given by

A. μ₁ = μsinβ

B. μ₁ = μcosβ

C. $${\mu _1} = \frac{\mu }{{\sin \beta }}$$

D. $${\mu _1} = \frac{\mu }{{\cos \beta }}$$

The lower pairs are _________ pairs.

A. Self-closed

B. Force-closed

C. Friction closed

D. None of these

In a coupling rod of a locomotive, each of the four pairs is a ________ pair.

A. Sliding

B. Turning

C. Rolling

D. Screw

A kinematic chain is known as a mechanism when

A. None of the links is fixed

B. One of the links is fixed

C. Two of the links are fixed

D. None of these