The GATE Grind

GATE 2018 ME (ME1) – Question 40

Theory of Machines · Gears and gear trains · 2 marks · Multiple choice

In the gear train shown, tooth counts are A = 20, B = 30, D = 20; C has 80 internal and 100 external teeth. Carrier AB is fixed. If A rotates clockwise at 300 rpm, D’s clockwise-positive speed is ______.

Diagram for GATE 2018 ME (ME1) question 40
  1. 240 rpm
  2. −240 rpm
  3. 375 rpm
  4. −375 rpm

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (C) 375 rpm

Explanation

Take clockwise positive. External A–B contact gives $\omega_B=-300(20)/30=-200$ rpm. Internal B–C contact gives $\omega_C=-200(30)/80=-75$ rpm. External C–D contact gives $\omega_D=-(-75)(100)/20=375$ rpm clockwise (C).