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Current Question (ID: 10315)

Question:
$\text{A uniform rod of length } l \text{ is hinged at one end and is free to rotate in the vertical plane. The rod is released from its position, making an angle } \theta \text{ with the vertical. The acceleration of the free end of the rod at the instant it is released is:}$
Options:
  • 1. $\frac{3g\sin\theta}{l}$
  • 2. $\frac{3g\cos\theta}{2}$
  • 3. $\frac{3g\sin\theta}{2}$
  • 4. $\frac{3g\cos\theta}{4}$
Solution:
\text{Hint: } \vec{\tau}_{\text{net}} = I\vec{\alpha} \text{Step 1: Use the torque equation for the rod.} \text{The rod is hinged at one end and makes an angle } \theta \text{ with the vertical. The weight } mg \text{ acts at the center of mass (at } \frac{l}{2} \text{ from the hinge). The perpendicular distance from the hinge to the line of action of weight is } \frac{l}{2}\sin\theta. \vec{\tau} = I\vec{\alpha} mg \cdot \frac{l}{2}\sin\theta = \frac{ml^2}{3}\alpha \alpha = \frac{3g\sin\theta}{2l} \text{Step 2: Find the acceleration of the free end of the rod assuming it is performing circular motion.} \text{For circular motion, the tangential acceleration at the free end is:} a_T = R\alpha \text{where } R = l \text{ (distance from hinge to free end)} a_T = l \times \frac{3g\sin\theta}{2l} = \frac{3g\sin\theta}{2} \text{At the instant of release, the tangential velocity } v_T = 0\text{, so the radial acceleration is zero. Therefore, the total acceleration of the free end is purely tangential and equals } \frac{3g\sin\theta}{2}.

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Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}