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 planet is revolving round the sun in an elliptical orbit. The maximum and the minimum distances of the planet from the sun are 3 \( \times \) \({\rm{1}}{0^{{\rm{12}}}}\) m and 2 \( \times \) \({\rm{1}}{0^{{\rm{10}}}}\) m respectively. The speed of the planet when it is nearest to sun is 2 \( \times \) \({\rm{1}}{0^{{\rm{7}}}}\) m/sec.what is the speed of the planet when it is farthest from the sun?
  • A
    3 \( \times \) \({\rm{1}}{0^{{\rm{5}}}}\) m/sec
  • B
    2.66 \( \times \) \({\rm{1}}{0^{{\rm{5}}}}\) m/sec
  • C
    1.5 \( \times \) \({\rm{1}}{0^{{\rm{7}}}}\) m/sec
  • D
    1.33 \( \times \) \({\rm{1}}{0^{{\rm{5}}}}\) m/sec
    Correct
2
The angular velocity of the body changes from \({\omega _{\rm{1}}}\) to \({\omega _{\rm{2}}}\) without applying torque but by changing moment of inertia. The ratio of initial radius of gyration to the final radius of gyration is
  • A
    \({\omega _{\rm{2}}}\): \({\omega _{\rm{1}}}\)
  • B
    \({\omega _{\rm{2}}}^{\rm{2}}\): \({\omega _{\rm{2}}}\)
  • C
    \(\surd \) ( \({\omega _{\rm{2}}}\)) : \(\surd \) ( \({\omega _{\rm{1}}}\))
    Correct
  • D
    (1 / \({\omega _{\rm{2}}}\)): (1/ \({\omega _{\rm{1}}}\))
3
Two bodies with moments of inertia I1 and I2 (I1\( > \) I2) have equal angular momenta. If K.E. of rotation are \({{\rm{E}}_{\rm{1}}}\) and \({{\rm{E}}_{\rm{2}}}\) then
  • A
    \({{\rm{E}}_{\rm{1}}}\) < \({{\rm{E}}_{\rm{2}}}\)
    Correct
  • B
    \({{\rm{E}}_{\rm{1}}}\) > \({{\rm{E}}_{\rm{2}}}\)
  • C
    \({{\rm{E}}_{\rm{1}}}\) = \({{\rm{E}}_{\rm{2}}}\)
  • D
    \({{\rm{E}}_{\rm{1}}}\) \( \ge \) \({{\rm{E}}_{\rm{2}}}\)
4
The moment of inertia of a thin uniform ring of mass 1 Kg about an axis passing through the centre and perpendicular to the plane of the ring is 0.25 Kg \({{\rm{m}}^{\rm{2}}}\).Then the diameter of the ring is
  • A
    1 m
    Correct
  • B
    0.25 m
  • C
    0.75 m
  • D
    0.5 m
5
We have two spheres, one is a hollow shell and the other a solid. They have identical masses and moments of inertia about their respective diameters. The ratio of their radii is given by
  • A
    it is 3: 5
  • B
    \(\surd \) (3) : \(\surd \) (5)
    Correct
  • C
    it is 5:7
  • D
    \(\surd \) (3) : \(\surd \) (7)
6
A particle performs uniform circular motion with an angular momentum L. If the frequency of particle's motion is doubled and its K.E. is halved, the angular momentum becomes
  • A
    4L
  • B
    L/4
    Correct
  • C
    L/2
  • D
    2L
7
A flywheel at rest is to reach an angular velocity of 36 rad/sec, in 6 sec, with a constant angular acceleration. The total angle turned during this interval is :
  • A
    72 rad
  • B
    108 rad
    Correct
  • C
    144 rad
  • D
    216 rad
8
The radius of gyration of a rod of mass 100 gm and length 100 cm about an axis passing through its centre of gravity and perpendicular to its length is given by
  • A
    \({{100} \over {\sqrt 3 }}\)
    Correct
  • B
    \({{50} \over {3\sqrt 2 }}\)
  • C
    \({{50} \over {2\sqrt 3 }}\)
  • D
    \({{100} \over {3\sqrt 3 }}\)
9
The M.I. of a body about a given axis is 1.2 kg \({{\rm{m}}^{\rm{2}}}\). Initially the body is at rest. In order to produce a rotational kinetic energy of 1500 joule, an angular acceleration of 25 rad/ \({\rm{se}}{{\rm{c}}^{\rm{2}}}\) must be applied about that axis for duration of
  • A
    4 sec
  • B
    2 sec
    Correct
  • C
    8 sec
  • D
    10 sec
10
A fan of moment of inertia 0.3 kg \({{\rm{m}}^{\rm{2}}}\)is to run up to a working speed of 0.5 revolution per second. Indicate the correct value of the angular momentum of the fan
  • A
    0.3 \(\pi \) kg \( \times \) \({{\rm{m}}^{\rm{2}}}\) / sec
    Correct
  • B
    (\(\pi \) /6) (kg \( \times \) \({{\rm{m}}^{\rm{2}}}\)) / sec
  • C
    3( kg \( \times \) \({{\rm{m}}^{\rm{2}}}\)) / sec
  • D
    6 kg \( \times \) \({{\rm{m}}^{\rm{2}}}\)/sec
11
Three thin uniform rods each of mass M and length L are placed along the three axis of a Cartesian coordinate system with one end of each rod at the origin. The M.I. of the system about z- axis is
  • A
    \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)/3
  • B
    \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)/6
  • C
    \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)
  • D
    (2/3) \({\rm{M}}{{\rm{L}}^{\rm{2}}}\)
    Correct
12
Two circular rings have their masses in the ratio 1:2 and their diameters in the ratio 2: 1. The ratio of their moments of inertia about their axes is
  • A
    it is 2 :1
  • B
    it is 2 : 1
    Correct
  • C
    it is 1: 4
  • D
    it is 4: 1
13
Four masses are fixed on a mass less rod as shown in figure. The moment of inertia about the axis P is about
Question 13 figure 1
  • A
    0.5 kg \({\rm{metr}}{{\rm{e}}^{\rm{2}}}\)
  • B
    0.3 kg \({\rm{metr}}{{\rm{e}}^{\rm{2}}}\)
  • C
    2 kg \({\rm{metr}}{{\rm{e}}^{\rm{2}}}\)
  • D
    1 kg \({\rm{metr}}{{\rm{e}}^{\rm{2}}}\)
    Correct
14
A wheel is rotating about an axis through its centre at 720 r.p.m. When acted upon by a constant torque opposing its motion for 8 seconds it stops rotating. The value of this torque in Nm is (given I =\({{24} \over \pi }\) kg \({{\rm{m}}^{\rm{2}}}\))
  • A
    96
  • B
    120
  • C
    48
  • D
    72.0
    Correct
15
A fly wheel rotating about a fixed axis has a kinetic energy of 360 joule when its angular speed is 30 radians per second. The moment of inertia of the fly wheel about the axis of rotation is
  • A
    0.75 kg \({{\rm{m}}^{\rm{2}}}\)
  • B
    0.6 kg \({{\rm{m}}^{\rm{2}}}\)
  • C
    0.15 kg \({{\rm{m}}^{\rm{2}}}\)
  • D
    0.8 kg \({{\rm{m}}^{\rm{2}}}\)
    Correct