Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
BITSAT 2022
Exam
BITSAT
Year
2022
Subject
Physics
Chapter
Rotational Motion

BITSAT 2022 · Physics · Rotational Motion

Four holes of radius 5 cm are cut from a thin square plate of 20 cm...

Four holes of radius 5cm5 \mathrm{ cm} are cut from a thin square plate of 20cm20 \mathrm{ cm} and mass 1kg1 \mathrm{ kg}. The moment of inertia of the remaining portion about ZZ-axis is Four holes of radius 5 cm are cut from a thin square plate of 20 cm and mass 1 kg . The moment of inertia of the

Options

  1. A15kg−m215 \mathrm{ kg}-\mathrm{m}^2
  2. B0.37kg−m20.37 \mathrm{ kg}-\mathrm{m}^2
  3. C0.0017kg−m20.0017 \mathrm{ kg}-\mathrm{m}^2
  4. D0.08kg−m20.08 \mathrm{ kg}-\mathrm{m}^2

Correct answer

C. 0.0017kg−m20.0017 \mathrm{ kg}-\mathrm{m}^2

Step-by-step solution

Area mass density, \sigma=\frac{M}{16 R^2}\left(\because \text{ Area }=4 R ×\times4 R=16 R²\right) Massofeachholem1=σπR2=M16R2πR2=πM16of each holem_1=\sigma \pi R^2=\frac{M}{16 R^2} \pi R^2=\frac{\pi M}{16} Distance between centre of plate and centre of hole x=(2R)2+(2R)22=22R2.<imgsrc="/api/proxy−image?url=https\frac{\sqrt{(2 R)^2+(2 R)^2}}{2}=\frac{2 \sqrt{2} R}{2} .<img src="/api/proxy-image?url=https%3A%2F%2Ffirebasestorage.googleapis.com%2Fv0%2Fb%2Fquantrexacademy-app.firebasestorage.app%2Fo%2Fquestions%252Ffigs%252Fpyq%252Fbitsat%252F48sXRImgpSV6Uufo34i1MCTn62UFM3A0DRF5amDDeHk.original.fullsize.png%3Falt%3Dmedia&clean=1&v=wm2" data-qx-orig-src="https://firebasestorage.googleapis.com/v0/b/quantrexacademy-app.firebasestorage.app/o/questions%2Ffigs%2Fpyq%2Fbitsat%2F48sXRImgpSV6Uufo34i1MCTn62UFM3A0DRF5amDDeHk.original.fullsize.png?alt=media" data-qx-storage-src="https://firebasestorage.googleapis.com/v0/b/quantrexacademy-app.firebasestorage.app/o/questions%2Ffigs%2Fpyq%2Fbitsat%2F48sXRImgpSV6Uufo34i1MCTn62UFM3A0DRF5amDDeHk.original.fullsize.png?alt=media"> \\ Moment of inertia of one hole at about Z-axis I_1=12\frac{1}{2}m_1 R²+m_1 x²=5π32\frac{5 \pi}{32}M R² Moment of inertia of whole plate about Z-axis, I=M(4R)26=83\frac{M(4 R)^2}{6}=\frac{8}{3}M R² Required moment of Inertia I_0=I-4 I_1,=\left[\frac{8}{3}-4\left(\frac{5 \pi}{32}\right)\right]MR2=[83−5π8]M R²=\left[\frac{8}{3}-\frac{5 \pi}{8}\right]M R² Given, R=5 cmR=5 \mathrm{~cm} and M=1 kgM=1 \mathrm{~kg} So, I0=[83−5π8]1×25×10−4=0.0017 kg−m2I_0=\left[\frac{8}{3}-\frac{5 \pi}{8}\right] 1 \times 25 \times 10^{-4}=0.0017 \mathrm{~kg}-\mathrm{m}^2
Practice Rotational Motion on Quantrex Academy →

More from Rotational Motion

The moment of inertia of a cube of mass m and side a about one of its edges is equal to BITSAT 2024The torque of a force 5 i +3 j -7 k about the origin is τ . If the force acts on a… BITSAT 2023A disc is rolling without slipping on a surface. The radius of the disc is R . At t=0… BITSAT 2023A solid sphere of 80 kg and radius 15 m moving in a space becomes a circular disc of… BITSAT 2022A round disc of moment of inertia I_ 2 about its axis perpendicular to its plane and… BITSAT 2021Three particles, each of mass m gram, are situated at the vertices of an equilateral… BITSAT 2021A solid cylinder and a hollow cylinder both of the same mass and same external diameter… BITSAT 2020M.I of a circular loop of radius R about the axis in figure is BITSAT 2020 Full Rotational Motion list All BITSAT PYQs