## Theory of Machine Open pairs are those which have

Two elements that permit relative motion
Point or line contact between the two elements when in motion
Elements of pairs not held together mechanically
Surface contact between the two elements when in motion

## Theory of Machine The example of completely constrained motion is a

Motion of a square bar in a square hole
Motion of a shaft with collars at each end in a circular hole
All of these
Motion of a piston in the cylinder of a steam engine

## Theory of Machine The unbalanced force due to reciprocating masses

Varies in magnitude and direction both
Varies in magnitude but constant in direction
Constant in magnitude and direction both
Varies in direction but constant in magnitude

Eight times
Sixteen times
Four times
Twice

## Theory of Machine The frictional torque transmitted in a flat collar bearing, considering uniform pressure, is (where r₁ and r₂ = External and internal radii of collar respectively)

(2/3). μ W (r₁ + r₂)
(1/2). μ W [(r₁³ - r₂³)/(r₁² - r₂²)]
(2/3). μ W [(r₁³ - r₂³)/(r₁² - r₂²)]
(1/2). μ W (r₁ + r₂)