Assertion A : If the ice on the polar caps of the earth melts, then length of the day will increase. Reason R : Moment of inertia of earth increases, as ice on polar caps melts. The correct answer is

Both A and R are true and R is the correct explanation of A

Both A and R are true but R is not the correct explanation of A

In a system of two particles of masses m 1 and m 2 the second particle is moved by a distance d towards the centre of mass. To keep the centre of mass unchanged, the first particle will have to be moved by a distance

m 2 m 1 d , towards the centre of mass.

m 2 m 1 d , away from the the centre of mass.

m 1 m 2 d , away from the centre of mass.

m 1 m 2 d , towards the centre of mass.

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Two loops $P$ and $Q$ are made from a uniform wire. The radii of $P$ and $Q$ are $r_{1}$ and $r_{2}$ respectively and their moments of inertia are $I_{1}$ and $I_{2}$ respectively. If $\frac{I_{2}}{I_{1}} = 4$ then, $\frac{r_{2}}{r_{1}}$ is equal to

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Important Questions on Motion of System of Particles and Rigid Body

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 23

Three thin uniform rods, each of mass

M

and length

L

, are placed along the three axes of a cartesian coordinate system with one end of each rod at the origin. The moment of inertia of the system about the

z

-axis will be,

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 24

The co-ordinate of the centre of mass of a system as shown in the figure is

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 25

Two rings of same radius and mass are placed such that their centres are at a common point and their planes are perpendicular to each other. The moment of inertia of the system about an axis passing through the centre and perpendicular to the plane of one of the rings is, (Mass of the ring

= m

, radius

= r

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 26

Three solid spheres of mass $M$ and radius $R$ are shown in the figure. The moment of inertia of the system about $x x'$ axis will be,

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 27

Two men $A$ and $B$ are standing on a plank. $B$ is at the middle of the plank and $A$ is at the left end of the plank. Surface of the plank is smooth. System is initially at rest and masses are as shown in the figure. $A$ and $B$ start moving such that the position of $B$ remains fixed with respect to the ground. Then, the point where $A$ meets $B$ is located at

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 28

A wheel is rotating about an axis through its centre at

720 rpm

. It is acted on by a constant torque opposing its motion for

8 s

to bring it to rest finally. The value of torque (in

N m

) is (Given:

I = \frac{24}{π} kg m^{2}

)

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 29

If the earth was to suddenly contract to

{\frac{1}{n}}^{th}

of its present radius without any change in its mass, then the duration of the new day will be nearly,

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Physics Crash Course NEET>Chapter 5 - Motion of System of Particles and Rigid Body>Level 3>Q 30

Two spheres

A

and

B

, each of mass

5 kg

, are joined on a light rod of length

1 m

at its ends. Considering these spheres as point masses, the ratio of moment of inertia about an axis through

A

and the middle point of rod perpendicular to it will be,

Two loops P and Q are made from a uniform wire. The radii of P and Q are r1 and r2 respectively and their moments of inertia are I1 and I2 respectively. If I2I1=4 then, r2r1 is equal to

Important Questions on Motion of System of Particles and Rigid Body

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Two loops $P$ and $Q$ are made from a uniform wire. The radii of $P$ and $Q$ are $r_{1}$ and $r_{2}$ respectively and their moments of inertia are $I_{1}$ and $I_{2}$ respectively. If $\frac{I_{2}}{I_{1}} = 4$ then, $\frac{r_{2}}{r_{1}}$ is equal to