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Question 30251
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Laws of Motion and Friction: Friction — Block on Block MCQ

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Friction — Block on BlockHardQuestion 30251

Question

A 2 kg block sits on a 5 kg block on a frictionless floor. μ between blocks = 0.3. A 10 N force on the bottom block. Do they move together? (g = 10 m/s²)
  1. A
    Yes, together at 1.43 m/s²
    Correct
  2. B
    No, they slip
  3. C
    Yes, together at 2 m/s²
  4. D
    Cannot determine

Correct answer

Yes, together at 1.43 m/s²

Explanation

If together: a = 10/7 ≈ 1.43 m/s². Friction needed on top block = 2×1.43 = 2.86 N. Max static friction = 0.3×2×10 = 6 N. Since 2.86 < 6, they move together at ≈ 1.43 m/s².

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