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GATE 2018 CE (CE2) – Question 39

Engineering Mechanics · System of forces, free-body diagrams, equilibrium equations · 2 marks · Multiple choice

Two rigid bodies of mass 5 kg and 4 kg are initially at rest on a frictionless surface. A 36 N force acts as shown. The contact force is ______.

Diagram for GATE 2018 CE (CE2) question 39
  1. 4.0 N
  2. 7.2 N
  3. 9.0 N
  4. 16.0 N

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Show answer and explanation

Correct answer: (D) 16.0 N

Explanation

The masses accelerate together at $a=36/(5+4)=4$ m/s². Contact is the only horizontal force on the 4 kg body, so $F=4(4)=16$ N (D).