Question

A palnar mechanism has 8 links and 10 rotary joints. The number of degrees of freedom of the mechanism, using Grubler’s criterion, is

(a) 0

(b) 1

(c) 2

(d) 3

I have been asked this question in a job interview.

My question is based upon Inversion of Mechanism in division Simple Mechanisms of Machine Kinematics

Answer 1

Right answer is (b) 1

For explanation: Whatever may be the number of links and joints Grubler’s criterion applies to mechanism with only single degree freedom. Subject to the condition 3I – 2J – 4 = 0 and it satisfy this condition.

Degree of freedom  is given by = 3(I – 1) – 2j = 3(8 -1) – (2×10) = 1.