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### Kennedy's Theorem Rule in Kinematics Formula and Calculator

Mechanics and Machine Design, Equations and Calculators

Kennedy's Theorem Rule in Kinematics Formula and Calculator

When three bodies move relative to one another, they have three instantaneous centers, all of which lie on the same straight line. Kennedy's theorem, which states that the number of ICs, c, for a given mechanism is related to the number of links, n, by:

c = n ( n - 1 ) / 2

Where

c = number of instantaneous centers, IC

n = number of links

Figure 1 - Three links (1,2, and 3) moving with respect to each other.

Click on image to enlarge

Source: Erdman, Arthur G., George N. Sandor, and Sridhar Kota, Mechanism Design, Vol. 1, 4th ed.,

New York: Prentice Hall, Inc.:

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