Question:

Vertical displacement of a plank with a body of mass m on it is varying according to law y = sin ω t + √(3)cos ω t. The minimum value of ω for which the mass just breaks contact with the plank and the moment it occurs first after t = 0, are given by

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Loss of contact occurs when downward acceleration equals g.
Updated On: Mar 20, 2026
  • \( \sqrt{g/2},\; \frac{\sqrt{2}\pi}{6\sqrt{g}} \)
  • \( \sqrt{g/2},\; \frac{2\pi}{3\sqrt{g}} \)
  • \( \sqrt{g/3},\; \frac{\pi}{3\sqrt{2/g}} \)
  • √(2g), (2π)/(3g)
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The Correct Option is A

Solution and Explanation


Step 1:
Resultant displacement: y = 2sin(ω t + (π)/(3))
Step 2:
Maximum downward acceleration: amax = 2ω²
Step 3:
For loss of contact: 2ω² = g ⟹ ω = √((g)/(2))
Step 4:
First occurrence after t=0: ω t + (π)/(3) = (3π)/(2) ⟹ t = frac√(2)π6√(g)
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