Theory Of Machine MCQ Questions & Answers | Mechanical Engineering

In a clock mechanism, both the hour hand and the minute hand rotate about the same central axis, but they rotate at different angular speeds (the minute hand completes one revolution per hour, while the hour hand completes one revolution in twelve hours).

A reverted gear train is specifically designed so that the input shaft and output shaft are coaxial, which is an essential requirement in clocks where both hands must be mounted on the same axis.

Although a simple gear train can transmit motion between gears, it generally does not satisfy the coaxial shaft requirement when multiple gears are needed to obtain the 12:1 speed reduction within a compact space.

A compound gear train can provide large speed ratios but the input and output shafts are not coaxial, making it unsuitable for clock hands.

An epicyclic gear train is used in applications like automatic transmissions and is unnecessarily complex for clock mechanisms.

Hence, the correct and standard answer in Theory of Machines is Reverted gear train.

Imagine a cam, that rotating part that makes other parts move up and down or back and forth.
It has a circular shape, but only a part of it is important for the actual movement.
This important part is called the pitch circle.
Now, imagine drawing a circle that goes through the pitch point (the point where the cam and the follower first touch).
And imagine that the center of this circle is exactly the same as the center of the cam's axis of rotation.
That special circle is called the prime circle.
So, a circle passing through the pitch point with its center at the center of cam axis is known as a prime circle.

A cylindrical cam is a type of cam where the follower moves along the surface of a rotating cylinder. The profile controlling the follower's motion is cut on the surface or end of the cylinder. Cylindrical cams are typically used when a translating or oscillating follower motion is required, guided by the groove on the cam's cylindrical surface.

Correct Answer: Option D – None of the above

Explanation:
Cams are mechanical elements used to convert rotary motion into linear or oscillatory motion. Based on geometry and motion, cams can be classified in different ways. Cylindrical cams specifically refer to cams where the follower moves parallel or perpendicular to the cam axis and follows a groove on the cylindrical surface.

Cylindrical cams are typically classified based on the type of follower motion (translating or oscillating) or based on the profile of the groove (helical, radial, etc.), but not as "circular" or "tangent".

The options given are unrelated to the standard classification of cylindrical cams:
Option A: Circular – This refers more to disc cams with circular profiles, not cylindrical cams.
Option B: Tangent – This is a term used for tangent or radial cam profiles, not for cylindrical cams.
Option C: Reciprocating – This refers to follower motion, not a classification of cams themselves.

Since none of the given options correctly represent types of cylindrical cams,

Conclusion:
The correct answer is Option D – None of the above.

When a rigid body is suspended vertically and it oscillates with a small amplitude under the action of the force of gravity, the body is known as

Option A: Simple pendulum
This option is not correct. A simple pendulum consists of a mass (called the pendulum bob) attached to a string or rod and swings back and forth under gravity. It is not a rigid body.

Option B: Compound pendulum
This is the correct answer. When a rigid body, such as a physical rod or a physical object, is suspended vertically and allowed to oscillate under gravity, it is referred to as a compound pendulum. The oscillation of the rigid body is similar in nature to that of a simple pendulum.

Option C: Torsional pendulum
A torsional pendulum is different from a compound pendulum. It consists of a rod or wire that is twisted and oscillates in torsional motion.

Option D: Second's pendulum
A Second's pendulum is a specific type of simple pendulum with a length such that it completes one full oscillation in exactly two seconds. It is not related to a rigid body.

Therefore, the correct answer is Option B: Compound pendulum.