# MCQ of System of Particles and Rotational Motion, Chapter 7, Class 11

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MCQ of  System of Particles and Rotational Motion, Chapter 7, Class 11, Physics

Multiple Choice Questions of System of Particles and Rotational Motion, Chapter 7, Class 11, Physics

Question 1 : Which of the following is the most appropriate statement about the centre of mass ?

1. The centre of mass always lies at the geometrical centre
2. The centre of mass always lie inside the body
3. The centre of mass always lie outside the body
4. The centre of mass may lie within or outside the body

Answer : D ( The centre of mass may lie within or outside the body )

Question 2 : What will be the position of centre of mass of a cube of uniform density

1. The centre of mass will be at the centre of one face
2. Centre of mass will be at the centre of interaction of diagonals of one face
3. The position of centre of mass will be at the geometric centre of the cube
4. The position of centre of mass will be at the edge of a cube

Answer : C ( The position of centre of mass will be at the geometric centre of the cube )

Question 3 : Two particles are having masses m and 2 m respectively. Then what will be the value of reduced mass of the two particles ?

1. The reduced mass of two particles is 2 m
2. The reduced mass of two particles is 3 m
3. The reduced mass of two particles is 2 m / 3
4. The reduced mass of two particles is m / 2

Answer : C ( The reduced mass of two particles is 2 m / 3 )

Question 4 : A rigid body is said to be in partial equilibrium if it is in

1. When it is in translational equilibrium only
2. When it is in rotational equilibrium only
3. Both a and b
4. Neither a nor b

Answer : C ( Both a and b )

Question 5 : A solid cylinder of radius R and mass M rolls on an inclined plane which is making an angle θ with the horizontal then calculate its acceleration

1. Acceleration is 1/3 g sinθ
2. Acceleration is 2/3 g sinθ
3. Acceleration is 2/5 g sinθ
4. Acceleration is 2/7 g sinθ

Answer B ( Acceleration is 2/3 g sinθ )

Question 6 : In the above question , how much force of friction is acting on the cylinder

1. Force of friction acting on cylinder is 2/3 Mg sinθ
2. Force of friction acting on cylinder is 1/3 Mg sinθ
3. Force of friction acting on cylinder is 2/5 Mg sinθ
4. Force of friction acting on cylinder is 2/7 Mg sinθ

Answer : B ( Force of friction acting on cylinder is 1/3 Mg sinθ )

Question 7 : Which of the following statement is inappropriate about rolling motion ?

1. During rolling motion , the instantaneous velocity of point if contact is negligible
2. During rolling motion , the instantaneous acceleration of point if contact is negligible
3. During rolling motion , work done against friction is negligible
4. If a wheel is moving down on an ideal frictionless surface , the wheel will slip only , but not roll on the floor .

Answer : B ( During rolling motion , the instantaneous acceleration of point if contact is negligible )

Question 8 : A body of mass M is rolling down an inclined plane which is making an angle of 60° with the horizontal . If the kinetic energy of rotation is equals to the 40% of kinetic energy in translatory state than the body is

1. It is a ring
2. It’s a cylinder
3. It is a hollow ball
4. It is a solid ball

Answer : D ( It is a solid ball )

Question 9 : Which of the following statements is mistaken about the rolling motion

1. Torque is the analogue of force in rotational motion
2. Rolling motion of a cylinder down an inclined plane which is making an angle O with the horizontal is a combination of rotational motion and the translational motion
3. If the effort arm is larger than the load arm then the mechanical advantage is smaller than 1
4. For a extended body , centre of mass and centre of gravity do not overlap each other

Answer : C ( If the effort arm is larger than the load arm then the mechanical advantage is smaller than 1 )

Question 10 :  A solid sphere rolls down two different inclined planes of same height but the angle of inclination is different for both of the inclined planes then in both cases

1. The speed and time of rolling down in both the cases will be same
2. The speed of rolling down the same but the time of this will be different.
3. The speed will be different but the time of rolling down will be same
4. The speed and time will be different in both the cases

Answer : B ( The speed of rolling down the same but the time of this will be different.)

You may also read MCQ of Physical World, MCQ of Units and Measurements, MCQ of Motion in a Straight Line, MCQ of Motion in a Plane, MCQ of Laws of Motion, MCQ of Work, Energy and PowerMCQ of Gravitation for better understanding of the chapters.

Question 11 : Where the angular momentum will be directed if an object of mass M is rotating about a fixed point

1. Angular momentum is directed along the radius
2. Angular momentum is directed along the tangent of the orbit
3. Angular momentum is directed along the line at angle of 45° to the plane of rotation
4. Angular momentum is directed along the axis of rotation

Answer : D ( Angular momentum is directed along the axis of rotation  )

Question 12 : What will be the amount of next torque acting on a body  if that angular momentum of a rotating body is conserved

1. Net torque is zero
2. Net torque is maximum
3. Net torque is minimum
4. Net torque is unity

Answer : A ( Net torque is zero )

Question 13 : If a flying wheel is rotating at a frequency of 420 rpm slows down at a constant rate of rad s-1 then how much time is required to stop that flying wheel ?

1. 22 s
2. 11 s
3. 44 s
4. 12 s

Answer : A ( 22 s )

Question 14 : Which is the correct analogue of mass in rotational motion

1. Moment of inertia is the analogue of mass in rotational motion
2. Torque is the analogue of mass in rotational motion
3. Radius of gyration is the analogue of mass in rotational motion
4. Angular momentum is analogue of mass in rotational motion

Answer : A ( Moment of inertia is the analogue of mass in rotational motion )

Question 15 : Which of the following quantities the moment of inertia depends on

1. Moment of inertia depends on the mass of body
2. Moment of inertia depends on the axis of rotation of the body
3. Moment of inertia depends on the shape and size of the body
4. All the three

Answer : D ( All the three )

Question 16 : Which of the following materials has the highest moment of inertia if each of them has the same radius ‘r’ and mass ‘m’ ?

1. A Ring has the highest moment of inertia about any of its diameter
2. A disc has the highest moment of inertia about any of its diameter
3. A hollow sphere about any of its diameter has the highest moment of inertia
4. A solid sphere about any of its diameter has the highest moment of inertia

Answer : C ( A hollow sphere about any of its diameter has the highest moment of inertia )

Question 17 : A person is having metals spheres in his hand and is standing on a rotating table if he withdraws his hand to his chest then what will be the effect on the angular velocity ?

1. Angular velocity increases
2. Angular velocity decreases
3. Angular velocity remain same
4. Can’t say

Answer : A ( Angular velocity increases )

Question 18 : 1. Center of gravity is the side at which the weight of a body acts
2. If the earth is assumed to have infinite large radius then the centre of mass coincide with the centre of gravity
3. To calculate the gravitational field intensity due to body and any external point the entire body can be considered to be concentrated at centre of gravity.
4. The radius of gyration is the length of perpendicular drawn from the centre of gravity of the body to axis

Which of the following statements are correct ?

1. (1) and (4)
2. (1) and (2)
3. (2) and (3)
4. (3) and (4)

Answer : A ( (1) and (4) )

Question 19 : What is the value of radius of gyration of a uniform rod of length L about an axis passing through one of its end and which is perpendicular to its length

1. L/√2
2. L/3
3. L/√3
4. L/2

Answer : C ( L/√3 )

Question 20 : Which is also known as moment of couple

1. Angular momentum is also known as moment of couple
2. Force is also known as moment of couple
3. Torque is also known as moment of couple
4. Impulse is also known as moment of couple

Answer : C ( Torque is also known as moment of couple )

Question 21 : A moment of couple produces

1. A couple produces a purely translation motion
2. A couple produces a purely rotational motion
3. A couple produces both translational and rotational motion
4. No motion is produced by a couple

Answer : B ( A couple produces a purely rotational motion )

Question 22 : Which of the following statement is incorrect about the equilibrium of a rigid body

1. A couple is a pair of equal and opposite forces with different lines of action
2. A couple produces only rotational motion without translational motion
3. A certain amount of couple is supplied when we open the lid of a bottle by turning it
4. Moment of couple depends on the site about which we take the moment

Answer : D ( Moment of couple depends on the site about which we take the moment )

Question 23 : Why is the angular momentum of a particle rotating with a central force is constant ?

1. It is due to constant torque
2. It is due to constant force
3. It is due to constant linear momentum
4. It is due to zero torque

Answer : D ( It is due to zero torque )

Question 24 : When does the velocity of centre of mass of the system remains constant

1. If the total external force acting on the system is minimum
2. If the total external force acting on the system is maximum
3. If the total external force acting on the system is unity
4. If the total external force acting on the system is zero

Answer : D ( If the total external force acting on the system is zero )

Question 25 : What is the direction of angular velocity vector

1. The direction of angular velocity vector is along the tangent to the circular path
2. The direction of angular velocity vector is along the inward radius
3. The direction of angular velocity vector is along the outward radius
4. The direction of angular velocity vector is along the axis of rotation

Answer : D ( The direction of angular velocity vector is along the axis of rotation )

Question 26 : Which of the following statements is appropriate about the linear velocity and the angular velocity ?

1. Linear momentum and velocity need not to be parallel for a general translational motion
2. Angular momentum and angular velocity are always parallel for a general rotational motion
3. Acceleration and velocity are always parallel for a general translational motion
4. Angular momentum and angular velocity and need not to be parallel four a general rotational motion

Answer : D ( Angular momentum and angular velocity and need not to be parallel four a general rotational motion )

Question 27 : An explosive shell travelling in a parabolic path suddenly explodes in the mid air then where will the centre of mass of the fragments move

1. The centre of mass of the fragments will move in vertically downwards direction
2. The centre of mass of the fragments will move along the original parabolic path
3. The centre of mass of the fragments will move in vertically upwards and then vertically downward direction .
4. The centre of mass of the fragments will move horizontally , followed by the parabolic path

Answer : B ( The centre of mass of the fragments will move along the original parabolic path )

Question 28 : Which of the following will be constant if it torque acting on a system is zero

1. Force will be constant
2. Linear impulse will be constant
3. Linear momentum will be constant
4. Angular momentum will be constant

Answer : D ( Angular momentum will be constant )

Question 29 : What will be the angular momentum w.r.t origin of an object of mass M moving with a constant velocity parallel to X – axis ?

1. Angular momentum is zero
2. Angular momentum remains constant
3. Angular momentum goes on increasing
4. Angular momentum goes on decreasing

Answer : B ( Angular momentum remains constant )

Question 30 : Which of the following relations is appropriate ?

4. None of these

Question 31 : A person is standing on a spinning stool with outstretched arms , if he suddenly brings his hands down , how will kinetic energy and angular momentum be affected ?

1. Both kinetic energy and angular momentum will increase
2. Both kinetic energy and angular momentum remains constant
3. Kinetic energy remains constant and angular momentum increases
4. Kinetic energy increases but angular momentum remains constant

Answer : D ( Kinetic energy increases but angular momentum remains constant )

Question 32 : The moment of inertia of a body A is IA and the moment of inertia of a body B is IB . If angular momentum of both the bodies is equal , then
( Given that the moment of inertia of A is greater than moment of inertia of B )

1. Kinetic energy of A will be equal to the kinetic energy of B
2. Kinetic energy of A will be greater than the kinetic energy of B
3. Kinetic energy of A will be lesser than the kinetic energy of B
4. Kinetic energy of two bodies cannot be compared by a given set data

Answer : C ( Kinetic energy of A will be lesser than the kinetic energy of B )

Question 33 : Three bodies a ring , a solid cylinder and a solid sphere starts from rest and are rolled down from the incline plane without slipping . Given that the radial of all the bodies are identical then which of the following bodies will reach the ground with maximum velocity ?

1. Ring will reach the ground with the maximum velocity
2. Solid cylinder will reach the ground with maximum velocity
3. Solid sphere will reach the ground with maximum velocity
4. All the bodies will reach the ground with same velocity

Answer : C ( Solid sphere will reach the ground with maximum velocity )

Question 34 : A solid sphere of mass M is rolled down without slipping an inclined  plane which is making an angle O with the horizontal . If initially the acceleration of the centre of mass is ‘a’ . What will be its acceleration is the same sphere slides without friction ?

1. 7 a/2
2. 5 a/2
3. 7 a/5
4. 5 a/2

Answer : C ( 7 a/5 )

Question 35 : A solid sphere of mass M is rolled down without slipping an inclined  plane which is making an angle O with the horizontal . What is the correct relation between O and μr

1. tanθ > 3μr
2. tanθ ≤ 3μr
3. tanθ < 3μr
4. None of these

Answer : B ( tanθ <= 3μr )

Question 36 : Which of the following principles a circus acrobat uses in his performance

1. The circus acrobat uses law of conservation of energy
2. The circus acrobat uses law of conservation of linear momentum
3. The circus acrobat uses law of conservation of mass
4. The circus acrobat uses law of conservation of angular momentum

Answer : D ( The circus acrobat uses law of conservation of angular momentum )

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