Question

A four bar mechanism is shown below.


For the mechanism to be a crank-rocker mechanism, the length of the link PQ can be

• A. 350 mm
• B. 200 mm
• C. 300 mm
• D. 80 mm

Answer 1

The correct option is D 80 mm


For the crank-rocker mechanism, the shortest link must be crank and adjacent to fixed as well as Grashoff's law must be satisfied.

If $l=80$ mm
then shortest will be = 80 mm
as well as $(80+600)<(400+300)$
$680<700$
Therefore law is satisfied.

$\Rightarrow$ $l=80$ mm