The ratio of the radii of gyration of a circular disc to that of

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 Multiple Choice QuestionsMultiple Choice Questions

111.

From a circular disc of radius R and mass 9M, a small disc of mass M and radius R/3 is removed concentrically. The moment of inertia of the remaining disc about an axis perpendicular to the plane of the disc and passing through its centre is

  • 40MR2/9

  • MR2

  • 4 MR2

  • 4 MR2

2046 Views

112.

A closely wound solenoid of 2000 turns and area of cross -section 1.5 x 10-4 m2 carries a current of 2.0 A. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 x 10-2 T making an angle of 30o with axis of  the solenoid. The torque on the solenoid will be

  • 3 x 10-3 N-m

  • 1.5 x 10-3 N-m

  • 1.5 x 10-2 N-m

  • 1.5 x 10-2 N-m

763 Views

113.

A thin circular ring of mass M and radius r is rotating about its axis with constant angular velocity ω. Two objects each of mass m are attached gently to the opposite ends of a diameter of the ring. The ring now rotates with angular velocity given by

  • (M +2m)ω /2m

  • 2Mω / M + 2m

  • (M +2m)ω / M

  • (M +2m)ω / M

650 Views

114.

Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle

  • depends on v and not on R

  • depends on R and not on v

  • is independent of both v and R

  • is independent of both v and R

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115.

A thin circular ring of mass M and radius R is rotating in a horizontal plane about an axis vertical to its plane with a constant angular velocity ω. If two objects each of mass m be attached gently to the opposite ends of a diameter of the ring. the ring will then rotate with an angular velocity

  • fraction numerator straight omega space left parenthesis straight M space minus 2 straight m right parenthesis over denominator straight M space plus space 2 straight m end fraction
  • fraction numerator ωM over denominator straight M space plus space 2 straight m end fraction
  • fraction numerator straight omega left parenthesis straight M space plus 2 straight m right parenthesis over denominator straight M end fraction
  • fraction numerator straight omega left parenthesis straight M space plus 2 straight m right parenthesis over denominator straight M end fraction
938 Views

116.

Four identical thin rods each of mass M and length l , inertial form a square frame. moment of inertia of this frame about an axis through the centre of the square and perpendicular to this plane is 

  • 4Ml2/3

  • 2Ml2/3

  • 13Ml2/3

  • 13Ml2/3

2228 Views

117.

A bar magnet having a magnetic moment of 2 x 104 JT-1 is free to rotate in a horizontal plane. A horizontal magnetic field B = 6 x 10-4 T exists in the space. The work  is done in taking the magnet slowly from a direction parallel to the field to a direction 60o from the field is

  • 0.6 J

  • 12 J

  • 6 J

  • 6 J

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118.

The ratio of the radii of gyration of a circular disc to that of a circular ring, each of same mass and radius, around their respective axes is 

  • square root of 3 colon square root of 2
  • 1 colon square root of 2
  • square root of 2 colon 1
  • square root of 2 colon 1


B.

1 colon square root of 2

The square root of the ratio of the moment of inertia of rigid body nad its mass is called radius of gyration.
As in key idea, radius of gyration is given by

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119.

A thin conducting ring and radius R is given charge +Q. The electric field at the centre O of the ring due to the charge on the part AKB of the ring is E. The electric field at the centre due to the charge on the part ACDB of the ring is 

  • 3E along KO

  • E along OK

  • E along KO

  • E along KO

1401 Views

120.

A thin rod of length L and Mass M is bent at its midpoint into two halves so that the angle between them is 90o. The moment of inertia of the bent rod about an axis passing through the bending point and perpendicular to the plane defined by the two halves of the rod is 

  • ML2/24

  • ML2/12

  • ML2/6

  • ML2/6

2690 Views

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