Theory of Machine
For a kinematic chain to be considered as mechanism

There is no such criterion
None of the links should be fixed
Two links should be fixed
One link should be fixed

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Theory of Machine
Angle of action of cam is defined as the angle

Moved by the cam from beginning of ascent to the termination of descent
Moved by the cam from the instant the follower begins to rise, till it reaches its highest position
Through which the cam rotates during the period in which the follower remains in the highest position
Of rotation of the cam for a definite displacement of the follower

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