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NEET 2015
Exam
NEET
Year
2015
Subject
Physics
Chapter
Rotational Motion

NEET 2015 · Physics · Rotational Motion

Three identical spherical shells, each of mass m and radius r are...

Three identical spherical shells, each of mass mm and radius rr are placed as shown in the figure. Consider an axis XX′X{X}^{′} which is touching the two shells and passing through the diameter of the third shell. The moment of inertia of the system consisting of these three spherical shells about XX′X{X}^{′} axis is:

Three identical spherical shells, each of mass m and radius r are placed as shown in the figure. Consider an axis X X ^

Options

  1. A115mr2\dfrac{11}{5}m{r}^{2}
  2. B3mr23m{r}^{2}
  3. C165mr2\dfrac{16}{5}m{r}^{2}
  4. D4mr24m{r}^{2}

Correct answer

D. 4mr24m{r}^{2}

Step-by-step solution

Three identical spherical shells, each of mass m and radius r are placed as shown in the figure. Consider an axis X X ^

Total moment of inertia of the system,
I+I1+I2+I3I + {I}_{1} + {I}_{2} + {I}_{3}
I2=I3=23mr2+mr2=5mr23{I}_{2} = {I}_{3} = \dfrac{2}{3}m{r}^{2} + m{r}^{2} = \dfrac{5m{r}^{2}}{3}
I1=23mr2{I}_{1} = \dfrac{2}{3}m{r}^{2}
∴ I = 2 × 5\dfrac{m{r}^{2}}{3} + \dfrac{2}{3}m{r}^{2}
I=12mr23=4mr2I = \dfrac{12m{r}^{2}}{3} = 4m{r}^{2}

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