Correct Answer - Option 3 : 3
Concept:
Degrees of freedom/mobility of a mechanism:
It is the number of inputs (number of independent coordinates) required to describe the configuration or position of all the links of the mechanism, with respect to the fixed link at any given instant.
According to Kutzbach criterion:
D.O.F = 3(L - 1) – 2j – h
where L is number of links, j is number of binary joints or lower pairs and h is number of higher pairs.
Revolute pair and prismatic pair are lower pairs.
Calculation:
Given:
L = 8; j = 9; h = 0
D.O.F = 3(L - 1) – 2j – h
D.O.F = 3 × (8 - 1) - (2 × 9) - 0 = 21 – 18 = 3
