MEDIUM
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A small ring is rolling without slipping on the circumference of a large bowl as shown below in the figure. The ring is moving down at P1, comes down to the lower most point P2 and is climbing up at P3. Let vCM denote the velocity of the centre of mass of the ring. Choose the correct statement regarding the frictional force on the ring.

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Important Questions on Centre of Mass, Momentum and Collisions

HARD
A uniform metal plate shaped like a triangle, ABC has a mass of 540 g. The length of the sides AB, BC and CA are 3 cm, 5 cm and 4 cm, respectively. The plate is pivoted freely about the point A. What mass must be added to a vertex so that the plate can hang with the long edge horizontal?
HARD
Distance of the centre of mass of a solid uniform cone from its vertex is z0. If the radius of its base is R and its height is h then z0 is equal to:
EASY
Two particles of mass m and 2m have their position vectors as a function of time as r1t=t i^-t3 j^+2t2 k^ and r1t=t i^-t3 j^-t2 k^ respectively (where t is the time). Which one of the following graphs represents the path of the centre of mass?
MEDIUM

The distance between the vertex and the centre, of mass of a uniform solid planar circular segment of angular size, θ and radius, R is given by

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MEDIUM
A smaller cube with side, b (depicted by dashed lines) is excised from a bigger uniform cube with side a as shown below, such that both cubes have a common vertex P. Let, X=ab. If the center of mass of the remaining solid is at the vertex O, of the smaller cube, then, X satisfies
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MEDIUM

The moments of inertia of a non-uniform circular disc (of mass M and radius R) about four mutually perpendicular tangents, AB, BC, CD, DA are I1, I2, I3 and I4, respectively (the square ABCD circumscribes the circle). The distance of the centre of mass of the disc from its geometrical centre is given by

HARD
A uniform square wooden sheet of side a has its center of mass located at the point, O as shown in the figure on the left. A square portion of side b of this sheet was cut out to produce as L-shaped sheet as shown in the figure on the right.
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The centre of mass of the L-shaped sheet lies at the point P (in the diagram) when
HARD

In the figure shown ABC is a uniform wire. If the center of mass of the wire lies vertically below point A, then BCAB is close to

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EASY
A man inside a freely falling box throws a heavy ball towards a sidewall. The ball keeps on bouncing between the opposite walls of the box. We neglect air resistance and friction. Which of the following figures depicts the motion of the center of mass of the entire system (man, the ball, and the box)?
MEDIUM

A hollow tilted cylindrical vessel of negligible mass rest on a horizontal plane as shown. The diameter of the base is a and the side of the cylinder makes an angle θ with the horizontal. Water is then slowly poured into the cylinder. The cylinder topples over when the water reaches a certain height h, given by
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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.
MEDIUM
A uniform thin rod AB of length L has linear mass density μx=a+bxL, where x is measured from A. If the CM of the rod lies at a distance of 712L from A, then a and b are related as:
HARD

Two identical objects each of radii, R and masses, m1 and, m2 are suspended using two strings of equal length, L as shown in the figure, (R<<L). The angle, θ which mass, m2 makes with the vertical is approximately

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HARD
A rigid body in the shape of a "V" has two equal arms made of uniform rods. What must the angle between the two rods be so that when the body is suspended from one end, the other arm is horizontal?
HARD

Two uniform plates of the same thickness and area but of different materials, one shaped like an isosceles triangle and the other shaped like a rectangle are joined together to form a composite body as shown in the figure alongside. If the centre of mass of the composite body is located at the mid-point of their common side, then the ratio between masses of the triangle to that of the rectangle is, 

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HARD

Four particles A, B, C  and D with masses mA=m,mB=2m,mC=3m  and mD=4m are at the corners of a square. They have accelerations of equal magnitude with directions as shown. The acceleration of the centre of mass of the particles is:
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HARD

Consider regular polygons with number of sides n=3,4,5 as shown in the figure. The center of mass of all the polygons is at height h from the ground. They roll on a horizontal surface about the leading vertex without slipping and sliding as depicted. The maximum increase in height of the locus of the center of mass for each polygon is Δ . Then, Δ depends on n and h as
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HARD
Two identical uniform rectangular blocks (with longest side L) and a solid sphere of radius R are to be balanced at the edge of a heavy table such that the centre of the sphere remains at the maximum possible horizontal distance from the vertical edge of the table without toppling as indicated in the figure.
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If the mass of each block is M and of the sphere is M2 , then the maximum distance x that can be achieved is
EASY
Two spherical bodies of mass M and 5M and radii R and 2R released in free space with initial separation between their centres equal to 12R. If they attract each other due to gravitational force only, then the distance covered by the smaller body before collision is:
MEDIUM
The position vector of the center of mass rcm  of an asymmetric uniform bar of negligible area of cross-section as shown in figure is:

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