EASY
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For a rigid circular body rotating about its axis with a constant angular speed, the magnitude of the velocity of particles situated at one of its radii:

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Important Questions on Motion of System of Particles and Rigid Body

MEDIUM
A ball of mass 100 g is dropped at time t=0. A second ball of mass 200 g is dropped from the same point at t=0.2 s. The distance between the center of mass of two balls and the release point at t=0.4 s is: (Assume g=10 m s-2)
HARD
The coordinates of the centre of mass of a uniform flag-shaped lamina (thin flat plate) of mass 4 kg. (The coordinates of the same are shown in the figure) are:

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MEDIUM
Two particles of mass 5 kg and 10 kg respectively are attached to the two ends of a rigid rod of length 1 m with negligible mass. The centre of mass of the system from the 5 kg particle is nearly at a distance of:
HARD

Figure below shows a shampoo bottle in a perfect cylindrical shape

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In a simple experiment, the stability of the bottle filled with different amount of shampoo volume is observed. The bottle is tilted from one side and then released. Let the angle θ depicts the critical angular displacement resulting in the bottle losing its stability and tipping over. Choose the graph correctly depicting the fraction f of shampoo filled (f=l corresponds to completely filled) vs the tipping angle θ.

HARD
Two stars of masses 3×1031 kg each, and at distance 2×1011 m rotate in a plane about their common centre of mass O. A meteorite passes through O moving perpendicular to the star's rotation plane. In order to escape from the gravitational field of this double star, the minimum speed that meteorite should have at O is ( Take Gravitational constant G=6.67×10-11 N m2 kg-2 )
HARD

A plank is moving in a horizontal direction with a constant acceleration ai^. A uniform rough cubical block of side l rests on the plank and is at rest relative to the plank.

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Let the centre of mass of the block be at 0, l2 at a given instant. If a=g10, then the normal reaction exerted by the plank on the block at that instant acts at

EASY
The centre of mass of a solid hemisphere of radius 8 cm is x cm from the centre of the flat surface. Then value of x is  
HARD

A wide bottom cylindrical massless plastic container of height 9 cm has 40 identical coins inside it and is floating on water with 3 cm inside the water. If we start putting more of such coins on its lid, it is observed that after N coins are put, its equilibrium changes from stable to unstable. Equilibrium in floating is stable if the geometric center of the submerged portion is above the center of mass of the object). The value of N is closest to

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MEDIUM
Which of the following statements are correct?

(i) Centre of mass of a body always coincides with the centre of gravity of the body.

(ii) Centre of mass of a body is the point at which the total gravitational torque on the body is zero

(iii) A couple on a body produce both translational and rotational motion in a body.

(iv) Mechanical advantage greater than one means that small effort can be used to lift a large load.
HARD

As shown in figure, when a spherical cavity (centred at O ) of radius 1 is cut out of a uniform sphere of radius R (centred at C ), the centre of mass of remaining (shaded part of sphere is at G, i.e., on the surface of the cavity. R can be determined by the equation:
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MEDIUM

Three point particles of masses 1.0 kg, 1.5 kg and 2.5 kg are placed at three corners of a right angle triangle of sides 4.0 cm, 3.0 cm and 5.0 cm as shown in the figure. The centre of mass of the system is at a point:
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MEDIUM
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 :
MEDIUM

A wheel of radius "rolls without slipping with a speed v on a horizontal road. When it is at a point A on the road a small bob of the mud separates from wheel at the highest point and touches the point B on the road as shown in the figure. Then AB is (g-acceleration due to gravity)

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MEDIUM

A rigid massless rod of length 3l has two masses attached at each end as shown in the figure. The rod is pivoted at point P on the horizontal axis. When released from the initial horizontal position, its instantaneous angular acceleration will be


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HARD
A body of mass m slides down an incline and reaches the bottom with a velocity. v. If the same mass were in the form of a ring which rolls down this incline. The velocity of the ring at the bottom would have been
MEDIUM
A rigid body is in pure rotation, that is undergoing fixed axis rotation. Then which of the following statements are true -
MEDIUM

In the figure A and B are identical blocks, each of mass m and C is a circular disc of equal mass m. Pulley is massless and ffictionless and thread is inextensible. Neglecting friction, find the acceleration of block A and B.
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HARD

A light thread has been tightly wrapped around a disc of mass M and radius R. The disc has been placed on a smooth table, lying flat as shown. The other end of the string has been attached to a mass m as shown. The system is released from rest. Find the acceleration of the disc and block.
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EASY

A uniform rod rotates in a vertical plane about the shown axis. Angular velocity at the moment is ω . Then, force on the rod by the axis at the moment
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EASY
A solid sphere, a hollow sphere and a ring are released from top of an inclined plane (frictionless) so that they slide down(no rolling) the plane. Then maximum acceleration down the plane is for