Theory of Machine
The Ackerman steering gear mechanism is preferred to the Davis steering gear mechanism, because

The Ackerman steering gear is most economical
The Ackerman steering gear consists of turning pairs
Whole of the mechanism in the Ackerman steering gear is on the back of the front wheels
Both (A) and (B)

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Theory of Machine
A rigid body, under the action of external forces, can be replaced by two masses placed at a fixed distance apart. The two masses form an equivalent dynamical system, if

The center of gravity of the two masses coincides with that of the body
The sum of the two masses is equal to the total mass of body
The sum of mass moment of inertia of the masses about their center of gravity is equal to the mass moment of inertia of the body
All of these

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