The minimum number of links in a constrained planer mechanism involving revolute pairs and two higher pairs is

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ESE Mechanical 2013 Official Paper - 2
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  1. 3
  2. 4
  3. 5
  4. 6

Answer (Detailed Solution Below)

Option 2 : 4
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Detailed Solution

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Concept: 

For a simple mechanism, the degree of freedom (F) is given by the Grubler’s criterion:

F = 3 (n - 1) - 2j - h

Where j = number of revolute joints

n = number of links

h = number of higher pairs

For a constrained planar mechanism, DOF is 1

⇒ 1 = 3 (n - 1) - 2j - 2 

⇒ 3n - 2j = 6

⇒ 2j = 3n - 6

The RHS of the equation should be positive and even number,

Put n = 3

2j = 3 × 3 - 6 = 3 odd

put n = 4

2j = 3 × 4 - 6 = 6 even

So, the minimum value of n should be 4

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