# 100+ System Of Particles And Rotational Motion MCQs and Answers

System Of Particles And Rotational Motion MCQs and Answers will be useful for various entrance exam like NEET, AIIMS, JEE. It includes an extensive section of physics and chemistry. These chapter covers each and every topic of System of Particles and Rotational Motion and more. It also contains chapter-wise MCQs with hints and options to make your preparation easy.

## System Of Particles And Rotational Motion MCQs and Answers

These System Of Particles And Rotational Motion MCQs and Answers are based on the following topics:

### System Of Particles And Rotational Motion MCQs

a) 10 N

b) 25/3π N

c) 50/3π N

d) 12.5/3 N

#### 4. The rate of change of angular speed is constant. What will be the expression for change in angular speed after time dt, if angular acceleration is ‘a’? The initial angular speed is ‘w’.

a) a*dt

b) w – a*dt

c) w + a*dt

d) There is no change

a) 25Nm

b) 2.5Nm

c) 12.5Nm

d) 1.25Nm

a) 1 kg

b) 1.5 kg

c) 2 kg

d) 2.5 kg

#### 8. Particles of masses 1 kg and 3 kg are at (2i+5j+13k) m and (-6i+4j-2k) m. What is the position of their centre of mass?

a) 1/4 (-16i + 17j + 7k) m

b) 1/4 (-8i + 17j + 7k) m

c) 1/4 (-6i + 17j + 7k) m

d) 1/4 (-6i + 17j + 5k) m

#### 9. The distance between the centres of carbon and oxygen in the carbon monoxide molecules is 1.13 x 10-10 m. The distance of the centre of mass of the molecule relative to the oxygen atom is _____

a) 0.48 x 10-10 m

b) 0.64 x 10-10 m

c) 0.56 x 10-10 m

d) 0.36 x 10-10 m

#### 10. Two particles of masses 2 kg and 3 kg are at rest and are separated by 10 m. If they move towards each other under the mutual force of attraction, they would meet at _____

a) 6 m from 4 kg body

b) 6 m from 6 kg body

c) 4 m from 4 kg body

d) 5 m from 6 kg body

a) 1.2 m

b) 2.4 m

c) 3.6 m

d) 4.8 m

#### 12. A uniform disc of radius R is put over another uniform disc of radius 2R of same thickness and density. The edges of the two discs touch each other. What is the position of their centre of mass?

a) at 5R/3 from the centre of the larger disc

b) at 2R/3 from the centre of the larger disc

c) at 3R/5 from the centre of the larger disc

d) at 2R/5 from the centre of the larger disc

a) R

b) 2R

c) 3R

d) 4R

a) 0.25 s

b) 0.05 s

c) 0.5 s

d) 1 s

#### 15. A solid sphere is given a horizontal velocity of 4m/s on a flat surface. What will be its velocity when it starts pure rolling? Mass = 2kg, Radius = 5cm. Coefficient of friction = 0.3.

a) It cannot roll purely

b) 2/3 s

c) 2s

d) 3s

#### 16. A ring is at the top of the incline of angle and height ‘h’. If it is left from rest and goes down rolling purely, find its speed at the bottom.

a) √ (2gh) m/s

b) √ (gh/sinθ) m/s

c) √ (ghsinθ) m/s

d) √ (gh) m/s

a) (Mgsinθ)/3

b) 0

c) (4Mgsinθ)/3

d) (2Mgsinθ)/3

a) 5m/s

b) 0m/s

c) 2.5m/s

d) 2m/s

#### 19. A disc is undergoing pure rolling motion on a flat surface. The radius of the disc is 5cm & velocity of centre of mass is 10m/s. What is the ratio of kinetic energy as seen from the ground frame to a frame moving along the disc with a speed of 10m/s?

a) 1:1, kinetic energy is frame independant

b) 3:1

c) 2:1

d) 1:3

a) R

b) πR

c) 2πR

d) 0

#### 21. The velocities of three particles of masses 10 kg, 20 kg and 30 kg are 10i, 10j and 10k m/s, respectively. What is the velocity of their centre of mass?

a) (i + 2j + 3k) m/s

b) 10 (i + j + k) m/s

c) (10i + 20j + 30k) m/s

d) (3i + 2j + k) m/s

a) a/4

b) a/2

c) a

d) 2a

a) 0

b) 0.8v

c) 80v

d) 8v

a)0 cm

b) 1 cm

c) 2 cm

d) 3 cm

a) 0m/s

b) 20m/s

c) 10m/s

d) 0.4m/s

a) 5.98m

b) 6.34m

c) 8.66m

d) 7.99m

a) 0s

b) 1s

c) 2s

d) 2.8s

a) 4.33 m/s

b) -4.33 m/s

c) -6.67 m/s

d) 6.67 m/s

#### 29. There are two external forces acting on a system of particles. Select the correct statement.

a) Linear momentum is necessarily not conserved

b) Linear momentum may be conserved

c) Linear momentum is zero

d) Centre of mass will move with increasing speed

#### 30. Which of the following is the mathematical representation of law of conservation of total linear momentum?

a) dP/dt = 0

b) dF/dt = 0

c) dP/dt = Finternal

d) dF/dt = P

#### 31. A ball of mass 2kg is moving with a speed of 10m/s along a flat surface. It collides with another ball of mass 3kg and comes to rest, what will be the speed of the second ball after collision?

a) The above said situation is not possible

b) 20m/s

c) Zero

d) 6.67m/s

a) v = r X w

b) v = w X r

c) v = w.r

d) w = v.r

#### 33. Which of the following statements is false?

a) Cross product is commutative

b) Cross product is distributive over addition

c) Dot product of two vectors gives a scalar

d) Dot product is commutative

#### 34. Find the vector product (a X b) of the two given vectors: a = 2i + 3j + 4k, b = 3i + 5j. Here, i, j & k are unit vectors along three mutually perpendicular axes.

a) -20i + 12j + k

b) 10i + 6j + 1/2k

c) 20i – 12j – k

d) 10i – 6j -1/2k

a) 0.00083kgm2

b) 0.0833kgm2

c) 0.0033kgm2

d) 0.00033kgm2

a) 16.67kgm2

b) 6kgm2

c) 10kgm2

d) 20kgm2

a) 1:1

b) 2:1

c) 1:2

d) 1:4

#### 38. Moment of inertia, of a spinning body about an axis, doesn’t depend on which of the following factors?

a) Distribution of mass around axis

b) Orientation of axis

c) Mass

d) Angular velocity

#### 39. Two cylinders have the same mass and radius. One is hollow and the other is solid. Which one will have the greater moment of inertia about the central axis?

a) Hollow cylinder

b) Solid cylinder

c) Same for both

d) Depends on length of cylinder

a) 1.414m

b) 0.707m

c) 1m

d) 1.732

a) 8kgm2

b) 16kgm2

c) 4kgm2

d) 2√2kgm2

#### 42. Let I1 be the moment of inertia about the centre of mass of a thick asymmetrical body. Let I2 be the moment of inertia about an axis parallel to I1. The distance between the two axes is ‘a’ & the mass of the body is ‘m’. Find the relation between I1 & I2.

a) I2 = I1 – ma2

b) I1 = I2 – ma2

c) I2 = I1

d) Parallel axis theorem can’t be used for a thick asymmetrical body

a) 0.75kgm2

b) 3kgm2

c) 5.25kgm2

d) 14.25kgm2

a) 2kgm2

b) 4kgm2

c) 8kgm2

d) 1kgm2

a) 10kgm2

b) 5kgm2

c) 20kgm2

d) 1kgm2

a) Iz = Ix + Iy

b) Ix = Ix + Iz

c) Iy = Ix + Iz

d) Iz = Ix = Iy

#### 47. Perpendicular axis theorem can be applied for which of the following bodies?

a) Ring having radius R & negligible cross section

b) Disc of radius R and thickness t

c) Cylinder of radius R and height h

d) A cube of side ‘a’

#### 48. Consider two perpendicular axis in the plane of a planar body, such that I1 = 2 I2. The moment of inertia about an axis perpendicular to the plane and passing through intersection of I1 & I2 is 9kgm2. Find the value of I1& I2.

a) I1 = 9kg m2, I2 = 4.5kgm2

b) I1 = 3kg m2, I2 = 6kg m2

c) I1 = 6kg m2, I2 = 3kg m2

d) I1 = 18kg m2, I2 = 9kg m2

a) 0.257s

b) 5s

c) 1.25s

d) 2.5s

a) 1.28W

b) 1.8W

c) 3.9W

d) 2.63W

#### 52. A rod is rotating about one end. If a force F1 acting on the other end produces a torque T & supplies power P, find the value of force F2 that will produce the same amount of power when it acts at the midpoint of the rod. Assume that all forces are perpendicular to the axis of rotation & axis of rod. The rod starts from rest.

a) = F1

b) > F1

c) < F1

d) No force acting at any other point will produce the same power

a) 0

b) 10.25Nm

c) 0.25Nm

d) 10Nm

a) 0.5/7π N

b) 35π N

c) 500/7π N

d) 0.7 N

#### 55. Which of the following quantities is zero if torque on a particle is zero?

a) Angular momentum of the particle

b) Angular speed of the particle

c) Change in kinetic energy of the particle

d) Rate of change of angular momentum

a) 0.1cm

b) 10cm

c) 5cm

d) 0.5m

#### 57. A disc is rotating with ω =10rad/s about a fixed central axis which is perpendicular to its plane. The disc has a mass =2kg & radius =10cm. A small particle of mass 100gm is put slowly on the disc’s outer circumference. There is sufficient friction between the disc and the particle. What will be the new angular velocity of the system?

d) Can’t conserve angular momentum because of friction

#### 58. A ring and a disc having masses in the ratio 1:2 are made to rotate about their central axes. Both are acted upon by the same torque when they are at rest. Which one will have more angular velocity when torque has been removed from both after the same time? Both have the same radius.

a) Ring

b) Disc

c) Same for both

d) Depends on ratio of mass and radius

a) True

b) False

#### 60. What is the rate of change of angular momentum?

a) Force

b) Torque

c) Work

d) Angular velocity