Theory of Machine
Lower pairs are those which have

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

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Theory of Machine
Hammer blow

Is the maximum vertical unbalanced force caused by the mass added to balance the reciprocating masses
Varies as the square root of the speed
Is the maximum horizontal unbalanced force caused by the mass provided to balance the reciprocating masses.
Varies inversely with the square of the speed

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