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
Rigid body is a body which
  • A
    deforms on application of force
  • B
    does not deform on the application of force
    Correct
  • C
    becomes longer or shorter if force is applied
  • D
    does not maintain the same distance between any two points on it if force is applied.
2
In pure translational motion of a rigid body
  • A
    at different instants of time every particle of the body has the same velocity.
  • B
    at any instant of time every particle of the body has the same velocity.
    Correct
  • C
    at any instant of time different particles of the body have different velocities.
  • D
    at any instant of time velocity is dependent on the position vector of a point on the body
3
in rotation of a rigid body about a fixed axis,.
  • A
    particles close to the axis have larger velocities
  • B
    every particle of the body moves in a circle, which lies in a plane perpendicular to the axis and has its centre on the axis
    Correct
  • C
    every particle of the body moves at the same speed
  • D
    every particle of the body moves in a ellipse, which lies in a plane perpendicular to the axis and has its focii on the axis
4
In precession such as that of a top
  • A
    the axis of rotation moves
    Correct
  • B
    the axis of rotation oscillates vertically
  • C
    the axis of rotation is fixed
  • D
    the axis of rotation oscillates horizontally
5
In a general motion of a rigid body
  • A
    both translation and rotation can be present
    Correct
  • B
    only translation is present
  • C
    particles on the body always move around an axis in circles
  • D
    only rotation is present
6
Let ri be the position vector of the ith particle having mass mi and R be the position vector of the centre of mass. The formula for R is
  • A
    \({\bf{R}} = {{\mathop \sum \nolimits^ {{\rm{m}}_{\rm{i}}}{{\bf{r}}_{\bf{i}}}} \over {\mathop \sum \nolimits^ {{\rm{m}}_2}}}\)
  • B
    \({\bf{R}} = {{\mathop \sum \nolimits^ {{\rm{m}}_{\rm{i}}}{{\bf{r}}_{\bf{i}}}} \over {\mathop \sum \nolimits^ {{\rm{m}}_1}}}\)
  • C
    \({\bf{R}} = {{\mathop \sum \nolimits^ {{\rm{m}}_{\rm{i}}}{{\bf{r}}_{\bf{i}}}} \over {\mathop \sum \nolimits^ {{\rm{m}}_3}}}\)
  • D
    \({\bf{R}} = {{\mathop \sum \nolimits^ {{\rm{m}}_{\rm{i}}}{{\bf{r}}_{\bf{i}}}} \over {\mathop \sum \nolimits^ {{\rm{m}}_{\rm{i}}}}}\)
    Correct
7
the centre of mass of a system of particles moves
  • A
    as if all the mass of the system was concentrated at the centre of mass and all the external forces were zero
  • B
    as if all the mass of the system was concentrated in a sphere around the centre of mass and all the external forces were zero
  • C
    as if all the mass of the system was concentrated at the axis of rotation and all the external forces were absent
  • D
    as if all the mass of the system was concentrated at the centre of mass and all the external forces were applied at that point
    Correct
8
The total momentum of a system of particles is equal to
  • A
    the product of the total mass of the system and the average velocity of its centre of mass
  • B
    the product of half the total mass of the system and the velocity of its centre of mass
  • C
    the product of the total mass of the system and the velocity of its centre of mass
    Correct
  • D
    the product of the total mass of the system and the speed of its centre of mass
9
considering binary (double) stars in our frame of reference, the trajectories of the stars are a combination of
  • A
    i) uniform motion in a straight line of the centre of mass and (ii) straight line motion of the stars about the centre of mass
  • B
    (i) uniform motion in a straight line of the centre of mass and (ii) circular orbits of the stars about the centre of mass
    Correct
  • C
    i) uniform motion in a straight line of the centre of mass and (ii) elliptical orbits of the stars about the centre of mass
  • D
    (i) uniform motion in a circle of the centre of mass and (ii) circular orbits of the stars about the centre of mass
10
The vector product of two vectors a and b is a vector c such that the magnitude of c is given by
  • A
    \(\left| {\mathbf{a}} \right|\left| {\mathbf{b}} \right|\)cos\(\theta \)
  • B
    \(\left| {\mathbf{a}} \right|\left| {\mathbf{b}} \right|\)sin\(\theta \)
    Correct
  • C
    \(\left| {\mathbf{a}} \right|\left| {\mathbf{b}} \right|\)tan\(\theta \)
  • D
    \(\left| {\mathbf{a}} \right|\left| {\mathbf{b}} \right|\)cot\(\theta \)
11
The vector product of two vectors a and b is a vector c such c is perpendicular to the plane containing a and b and the direction is given by is given by
  • A
    left hand rule
  • B
    left handed screw rule
  • C
    index finger rule
  • D
    right handed screw rule
    Correct
12
If \({\bf{a}} = {{\rm{a}}_{\rm{x}}}{\bf{\hat i}} + {{\rm{a}}_{\rm{y}}}{\bf{\hat j}} + {{\rm{a}}_{\rm{z}}}{\bf{\hat k}}{\rm{and}}{\bf{b}} = {{\rm{b}}_{\rm{x}}}{\bf{\hat i}} + {{\rm{b}}_{\rm{y}}}{\bf{\hat j}} + {{\rm{b}}_{\bf{z}}}{\bf{\hat k}}\) then the cross product \({\mathbf{a}} \times {\mathbf{b}}\) is given by
  • A
    \(\left| {\begin{array}{*{20}{c}} {{\mathbf{\hat i}}}&{{\mathbf{\hat j}}}&{{\mathbf{\hat k}}} \\ {{{\text{a}}_{\text{x}}}}&{{a_y}}&{{a_z}} \\ {{b_x}}&{{b_y}}&{{b_z}} \end{array}} \right|\)
    Correct
  • B
    \(\left| {\begin{array}{*{20}{c}} {{\mathbf{\hat i}}}&{{\mathbf{\hat j}}}&{{\mathbf{\hat k}}} \\ {{{\text{a}}_{\text{x}}}}&{{a_y}}&{{a_z}} \\ {{b_x}}&{{b_x}}&{{b_z}} \end{array}} \right|\)
  • C
    \(\left| {\begin{array}{*{20}{c}} {{\mathbf{\hat i}}}&{{\mathbf{\hat j}}}&{{\mathbf{\hat k}}} \\ {{{\text{a}}_{\text{x}}}}&{{a_x}}&{{a_z}} \\ {{b_x}}&{{b_x}}&{{b_z}} \end{array}} \right|\)
  • D
    \(\left| {\begin{array}{*{20}{c}} {{\mathbf{\hat i}}}&{{\mathbf{\hat j}}}&{{\mathbf{\hat k}}} \\ {{{\text{a}}_{\text{x}}}}&{{a_y}}&{{a_z}} \\ {{b_x}}&{{b_y}}&{{b_x}} \end{array}} \right|\)
13
If a body is rotating about z axis with a speed \(\omega \) and a point is at a distance of r in the x-y plane then the velocity of the point is
  • A
    \(r\omega /2\)
  • B
    \(3r\omega \)
  • C
    \(2r\omega \)
  • D
    \(r\omega \)
    Correct
14
The moment of inertia of a body about any axis is
  • A
    equal to the difference of the moment of inertia of the body about a parallel axis passing through its centre of mass and the product of its mass and the square of the distance between the two parallel axes.
  • B
    equal to the average of the moments of inertia of the body about a parallel axis passing through its centre of mass and the product of its mass and the square of the distance between the two parallel axes.
  • C
    equal to the sum of the moment of inertia of the body about a parallel axis passing through its centre of mass and the product of its mass and the square of the distance between the two parallel axes.
    Correct
  • D
    equal to the sum of the moment of inertia of the body about any axis passing through its centre of mass and the product of its mass and the square of the distance between the two parallel axes.
15
Angular acceleration vector is defined as
  • A
    \(\alpha = {{{d^3}\omega } \over {d{t^3}}}\)
  • B
    \(\alpha = {{{d^2}\omega } \over {d{t^2}}}\)
  • C
    \(\alpha = {{d\omega } \over {dt}}\)
    Correct
  • D
    \(\alpha = 2{{d\omega } \over {dt}}\)