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ABC is a plane lamina of the shape of an equilateral triangle. D, E are mid-points of AB, AC and G is the centroid of the lamina. Moment of inertia of the lamina about an axis passing through G and perpendicular to the plane ABC is I0. If part ADE is removed, the moment of inertia of the remaining part about the same axis is NI016 where N is an integer. Value of N is:

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Important Questions on Rotational Motion

MEDIUM
JEE Main
IMPORTANT
A circular disc of mass M and radius R is rotating about its axis with angular speed ω1. If another stationary disc having radius R2 and same mass M is dropped co-axially on to the rotating disc. Gradually both discs attain constant angular speed ω2. The energy lost in the process is p% of the initial energy. Value of p is _____.
MEDIUM
JEE Main
IMPORTANT
Consider two uniform discs of the same thickness and different radii  R1=R and R2=αR made of the same material. If the ratio of their moments of inertia I1 and I2, respectively, about their axes is I1:I2=1:16 then the value of α is :
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For a uniform rectangular sheet shown in the figure, the ratio of moments of inertia about the axes perpendicular to the sheet and passing through O (the centre of mass) and O' (corner point) is:

MEDIUM
JEE Main
IMPORTANT
A wheel is rotating freely with an angular speed ω on a shaft. The moment of inertia of the wheel is I and the moment of inertia of the shaft is negligible. Another wheel of moment of inertia 3I initially at rest is suddenly coupled to the same shaft. The resultant fractional loss in the kinetic energy of the system is:
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JEE Main
IMPORTANT
A force F=(i^+2j^+3k^) N acts at a point (4i^+3j^-k^) m. Then the magnitude of torque about the point (i^+2j^+k^) m will be x  N m.The value of x is..........
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JEE Main
IMPORTANT

A thin rod of mass 0.9 kg and length 1 m is suspended, at rest, from one end so that it can freely oscillate in the vertical plane. A particle of mass 0.1 kg moving in a straight line with velocity 80 m s-1 hits the rod at its bottom most point and sticks to it (see figure). The angular speed (in rad s-1) of the rod immediately after the collision will be …………

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MEDIUM
JEE Main
IMPORTANT

Shown in the figure is a hollow ice-cream cone (it is open at top). If its mass is M, radius of its top is R and height, H, then its moment of inertia about its axis is

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MEDIUM
JEE Main
IMPORTANT

Four point masses, each of mass m, are fixed at the corners of a square of side I. The square is rotating with angular frequency ω, about an axis passing through one of the corners of the square and parallel to the diagonal, as shown in the figure. The angular momentum of the square about the axis is

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