System Of Particles And Rotational Motion CBSE Questions & Answers

System Of Particles And Rotational Motion

This is Physics Class 11 System of Particles and Rotational Motion CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
A body of mass 2.0 kg and radius of gyration 0.5 m is rotating about an axis. If its angular speed is 2.0 rad/s, the angular momentum of the body (in kg - \({{\rm{m}}^{\rm{2}}}\)/s) is
  • A
    0.5
  • B
    1.0
    Correct
  • C
    2.0
  • D
    1.5
2
The angular velocity of a body changes form 1 rev. /25 sec. to 1 rev/sec. without applying any external torque. The ratio of the radii of gyration in the two cases is
  • A
    it is 1: 5
  • B
    it is 1: 25
  • C
    it is 25:1
  • D
    it is 5:1
    Correct
3
The angular velocity of a body changes form 1 rev/16 sec. to 1 rev/sec. without applying any external torque. The ratio of its radius of gyration in the two cases is
  • A
    it is 4: 1
    Correct
  • B
    it is 1:16
  • C
    it is 16:1
  • D
    it is 1:4
4
A body having moment of inertia about its axis equal to 3 kg \({{\rm{m}}^{\rm{2}}}\) is rotating with angular velocity equal to 3 rad/s. The kinetic energy of this rotating body is the same as that of a body of mass 27 kg moving with a speed of
  • A
    1.5 m/s
  • B
    1.0 m/s
    Correct
  • C
    2.0 m/s
  • D
    0.5 m/s
5
The moment of inertia of a solid sphere about a diameter is 8000 gms \({\rm{c}}{{\rm{m}}^{\rm{2}}}\) (mass of sphere = 50 gm, radius = 20 cm). The moment of inertia about a tangent will be
  • A
    280 gm \({\rm{c}}{{\rm{m}}^{\rm{2}}}\)
  • B
    2.8 \( \times \) \({\rm{1}}{0^{\rm{4}}}\) gm \({\rm{c}}{{\rm{m}}^{\rm{2}}}\)
    Correct
  • C
    8400 gm \({\rm{c}}{{\rm{m}}^{\rm{2}}}\)
  • D
    2.8 \( \times \) \({\rm{1}}{0^{\rm{3}}}\) gm \({\rm{c}}{{\rm{m}}^{\rm{2}}}\)
6
A particle moves with a constant velocity parallel to the x - axis. Its angular momentum with respect to the origin
  • A
    remains constant
    Correct
  • B
    is zero
  • C
    goes on decreasing
  • D
    goes on increasing
7
If the radius of earth contracts to half of its present value, the mass remaining unchanged, the duration of the day will be
  • A
    24 Hrs
  • B
    48 hrs
  • C
    6 hrs
    Correct
  • D
    12 Hrs
8
A boy comes running and sits on a merry-go-round. What is conserved?
  • A
    Linear momentum
  • B
    None of these
  • C
    Kinetic energy of rotation
  • D
    Angular momentum
    Correct
9
A ring of radius r and mass m rotates about its central axis. The kinetic energy is
  • A
    mr \({\omega ^2}\) /2
  • B
    mr \({\omega ^2}\)
  • C
    \({\rm{m}}{{\rm{r}}^{\rm{2}}}\) \({\omega ^2}\) /2
    Correct
  • D
    \({\rm{m}}{{\rm{r}}^{\rm{2}}}\) \({\omega ^2}\)
10
A thin circular ring of mass M and radius R is rotating about its central axis with angular velocity. Four point objects each of mass m are attached gently to the opposite ends of two perpendicular diameters, the angular velocity of the ring is given by
  • A
    \({M \over {M + 4m}} \cdot \omega \)
    Correct
  • B
    \({M \over {M + m}} \cdot \omega \)
  • C
    \({{M + 4m} \over M} \cdot \omega \)
  • D
    \({{M - 4m} \over {M + 4m}} \cdot \omega \)
11
What is the moment of inertia of a thin rod of length L and mass M about an axis passing through one end and perpendicular to its length?
  • A
    \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)
  • B
    \({1 \over 12}\) \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)
  • C
    \({1 \over 3}\) \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)
    Correct
  • D
    \({1 \over 2}\) \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)
12
The radius of gyration of a solid disc about one of its diameter is given by
  • A
    \({R \over 2}\)
    Correct
  • B
    \(\sqrt {2} \)R
  • C
    2R
  • D
    \({R \over {\sqrt 2 }}\)
13
The moment of inertia of a solid sphere of density \(\rho \) and radius R is given by
  • A
    None of these
  • B
    \({{176} \over {105}}\rho {R^2}\)
  • C
    \({{105} \over {176}}\rho {R^2}\)
  • D
    \({{176} \over {105}}\rho {R^5}\)
    Correct
14
A thin uniform rod of length 2l and mass M is acted upon a constant torque. The angular velocity changes from zero to \(\omega \) in time t. The value of torque is
  • A
    \({{M{l^2}\omega } \over {3t}}\)
    Correct
  • B
    \({{M{l^2}\omega } \over {12t}}\)
  • C
    \({{M{l^2}\omega } \over t}\)
  • D
    \({{2M{l^2}\omega } \over {3t}}\)
15
A particle is orbiting in a vertical plane. Its linear momentum will be directed
  • A
    horizontally
  • B
    tangential to the orbit
    Correct
  • C
    at 45\(^\circ \) to the vertical
  • D
    vertically