The GATE Grind

GATE 2025 ME – Question 29

Theory of Machines · Balancing of reciprocating and rotating masses · 1 mark · Multiple choice

In the context of balancing of rotating and reciprocating masses, which one of the following options is true?

  1. An unbalanced rigid rotor can be completely balanced using a single balancing mass
  2. An unbalanced rigid rotor can be completely balanced using two balancing masses attached in two distinct planes
  3. A single-cylinder internal combustion engine can be completely balanced using a single balancing mass
  4. A single-cylinder internal combustion engine can be completely balanced using two balancing masses

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Show answer and explanation

Correct answer: (B) An unbalanced rigid rotor can be completely balanced using two balancing masses attached in two distinct planes

Explanation

A rigid rotor with an unbalance in both force and couple can be fully balanced by placing two masses in two different planes. A single mass can balance only the force. A single-cylinder reciprocating engine can never be balanced completely, because the unbalanced force changes with the crank angle.