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JEE Main 2024 (8 Apr, Shift 1) · Composite & Cut-Out Bodies

Composite & Cut-Out Bodies question from JEE Main 2024 (8 Apr, Shift 1)

Q5JEE Main 2024 · 8 APR · SHIFT 1Medium

Composite & Cut-Out Bodies

A uniform thin metal plate of mass 10 kg10\text{ kg} with dimensions is shown. The ratio of xx and y coordinates of center of mass of plate is n9\frac{n}{9}. The value of nn is ________.

Figure

Numerical answer type. Work it out, then open the answer.

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Answer: 15

  1. Plate = full rectangle 3×23\times 2 (area 66, centre (1.5, 1)(1.5,\ 1)) minus square 1≤x≤2, 1≤y≤21\le x\le 2,\ 1\le y\le 2 (area 11, centre (1.5, 1.5)(1.5,\ 1.5)).
  2. The shape is symmetric about x=1.5x = 1.5, so xcm=1.5x_{cm} = 1.5.
  3. ycm=6(1)−1(1.5)6−1=4.55=0.9y_{cm} = \frac{6(1) - 1(1.5)}{6-1} = \frac{4.5}{5} = 0.9
  4. xcmycm=1.50.9=53=159\frac{x_{cm}}{y_{cm}} = \frac{1.5}{0.9} = \frac{5}{3} = \frac{15}{9}
  5. So n=15n = 15.
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