# Mechanical Engineering - Theory of machines

### Exercise :: Theory of machines - Section 1

36.

The sliding pairs, turning pairs and screw pairs form lower pairs.

 A. True B. False

Explanation:

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37.

When a particle moves round the circumference of a circle of radius r with ω rad/s, then its maximum acceleration is ω2r.

 A. Right B. Wrong

Explanation:

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38.

The static friction

 A. bears a constant ratio to the normal reaction between the two surfaces B. is independent of the area of contact, between the two surfaces C. always acts in a direction, opposite to that in which the body tends to move D. all of the above

Explanation:

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39.

A shaft has an attached disc at the centre of its length. The disc has its centre of gravity located at a distance of 2 mm from the axis of the shaft. When the shaft is allowed to vibrate in its natural bow-shaped mode, it has a frequency of vibration of 10 rad/s. When the shaft is rotated at 300 r.p.m., it will whirl with a radius of

 A. 2 mm B. 2.22 mm C. 2.50 mm D. 3.0 mm

Explanation:

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40.

The swaying couple is maximum or minimum when the angle of inclination of the crank to the line of stroke (θ) is equal to

 A. 90° and 180° B. 45° and 225° C. 180° and 270° D. 270° and 360°