A round bar in a round hole form a turning pair

A square bar in a square hole form a sliding pair

A vertical shaft in a foot step bearing forms a successful constraint

all of the above

60 to 80 r.p.m.

80 to 100 r.p.m.

100 to 200 r.p.m.

200 to 300 r.p.m.

length of pair of contact to the circular pitch

length of arc of contact to the circular pitch

length of arc of approach to the circular pitch

length of arc of recess to the circular pitch

Scott-Russell's mechanism

Hart's mechanism

Peaucellier's mechanism

all of these

increases

decreases

remains unaffected

first increases and then decreases