Theory of Machine
The displacement of a flat faced follower when it has contact with the flank of a circular arc cam, is given by (where R = Radius of flank, r₁ = Minimum radius of the cam, and θ = Angle turned through by the cam)

(R - r₁) (1 - cosθ)
(R - r₁) (1 - sinθ)
R (1 - sinθ)
R (1 - cosθ)

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Theory of Machine
Lower pairs are those which have

Two elements that permit relative motion
Elements of pairs not held together mechanically
Point or line contact between the two elements when in motion
Surface contact between the two elements when in motion

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