NEET Physics Centre of Mass Centre of Gravity and Principle of Moments MCQs Set A

a) may lie within, outside on the surface of the body

b) lies always inside the body

c) lies always on the surface of the body

d) lies always outside the body

Answer: may lie within, outside on the surface of the body

Question:  Position vector of centre of mass of two particles system is given by

a)

b)

c)

d)

Answer:

Question: The position of centre of mass of a system of particles does not depend upon the

a) relative distance between the particles

b) position of the particles

c) symmetry of the body

d) mass of particles

Answer: relative distance between the particles

Question:

a)

b)

c)

d)

Answer:

Question: The motion of the centre of mass depends on

a) total external forces

b) total internal forces

c) Both

d) None of these

Answer: total external forces

Question: The centre of mass of two particles lies on the line

a) joining the particles

b) perpendicular to the line joining the particles

c) at any angle to this line

d) None of these

Answer: joining the particles

Question: A pulley fixed to the ceiling carries a string with blocks of mass m and 3 m attached to its ends. The masses of string and pulley are negligible. When the system is released, its centre of mass moves with what acceleration ?

a) g/2

b) – g/2

c) – g/4

d) 0

Answer: g/2

Question: In rotatory motion, linear velocities of all the particles of the body are

a) different

b) zero

c) cannot say

d) same

Answer: different

Question:

a)

b)

c)

d) None of these

Answer:

Question:  Two spheres A and B of masses m and 2m and radii 2R and R respectively are placed in contact as shown. The COM of the system lies

a) at the point of contact

b) inside B

c) inside A

d) None of these

Answer: at the point of contact

Question:  The motion of a rigid body which is not pivoted or fixed in some way is either a pure ...A... or a combination of translation and rotation. The motion of a rigid body which is pivoted or fixed in some way is ...B... Here, A and B refer to

a) translation and rotation

b) rotation and translation

c) translation and the combination of rotation and translation

d) None of the above

Answer: translation and rotation

Question: If the resultant of all external forces is zero, then velocity of centre of mass will be

a) either (a) or (b)

b) zero

c) constant

d) neither (a) nor (b)

Answer:  either (a) or (b)

Question: In rotation of a rigid body about a fixed axis, every ...A...of the body moves in a ...B..., which lies in a plane ...C... to the axis and has its centre on the axis. Here, A, B and C refer to

a) particle, circle and perpendicular

b) particle perpendicular and perpendicular

c) circle, particle and perpendicular

d) particle, perpendicular and circle

Answer: particle, circle and perpendicular

Question: Centre of mass of the earth and the moon system lies

a) closer to the earth

b) closer to the moon

c) at the mid-point of line joining the earth and the moon

d) cannot be predicted

Answer:  closer to the earth

Question: Consider the following statements and choose the correct option.
I. Position vector of centre of mass of two particles of equal mass is equal to the position vector of either particle.
II. Centre of mass is always at the mid-point of the line joining two particles
III. Centre of mass of a body can lie where there is no mass

a) III only

b) I, II and III

c) II only

d) I and II

Answer: III only

Question: There are some passengers inside a stationary railway compartment. The centre of mass of the compartment itself (without the passengers) is C₁, while the centre of mass of the ‘compartment plus passengers’ system is C₂. If the passengers move about inside the compartment then

a) C₁ will move but C₂ will be stationary with respect to the ground

b) C₂ will move but C₁ will be stationary with respect to the ground

c) neither C₁ nor C₂ will be stationary with respect to the ground

d) both C₁ and C₂ will move with respect to the ground

Answer:  C₁ will move but C₂ will be stationary with respect to the ground

Question: A stick is thrown in the air and lands on the ground at some distance from the thrower. The centre of mass of the stick will move along a parabolic path

a) in all cases

b) only if the stick is uniform

c) only if the stick has linear motion but no rotational motion

d) only if the stick has a shape such that its centre of mass is located at some point on it and not outside it

Answer: in all cases

Question:  The motion of binary stars , S₁ and S₂ is the combination of ....X.... and ....Y.... . Here, X and Y refer to

a) motion of the CM and motion about the CM

b) motion about the CM and motion of one star

c) position of the CM and motion of the CM

d) motion about CM and position of one star

Answer: motion of the CM and motion about the CM

More Questions.........................................

Question: Assertion : The centre of mass of a two particle system lies on the line joining the two particle, being closer to the heavier particle.
Reason : Product of mass of particle and its distance from centre of mass is numerically equal to product of mass of other particle and its distance from centre of mass.

a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.

b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

c) Assertion is correct, reason is incorrect

d) Assertion is incorrect, reason is correct.

Answer: Assertion is correct, reason is correct; reason is a correct explanation for assertion.

Question:  Consider a system of two particles having masses m₁ and m₂ . If the particle of mass m1 is pushed towards the centre of mass particles through a distance d, by what distance would the particle of mass m₂ move so as to keep the mass centre of particles at the original position?

a)

b)

c)

d) d

Answer:

Question: Three masses are placed on the x-axis : 300 g at origin, 500 g at x = 40 cm and 400 g at x = 70 cm. The distance of the centre of mass from the origin is

a) 40 cm

b) 45 cm

c) 50 cm

d) 30 cm

Answer:  40 cm

Question:

a) does not shift

b) depends on height of breaking

c) towards body B

d) towards body C

Answer: does not shift

Question: Assertion : The centre of mass of an isolated system has a constant velocity.
Reason : If centre of mass of an isolated system is already at rest, it remains at rest.

a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

b) Assertion is correct, reason is correct; reason is a correct explanation for assertion.

c) Assertion is correct, reason is incorrect

d) Assertion is incorrect, reason is correct

Answer:  Assertion is correct, reason is correct; reason is not a correct explanation for assertion

Question:

a) remains at rest

b) None of these

c) move towards m₂

d) move towards m₁

Answer: remains at rest

Question: A shell following a parabolic path explodes somewhere in its flight. The centre of mass of fragments will continue to move in

a) same parabolic path

b) any direction

c) vertical direction

d) horizontal direction

Answer: same parabolic path

Question: A man stands at one end of a boat which is stationary in water. Neglect water resistance. The man now moves to the other end of the boat and again becomes stationary. The centre of mass of the ‘man plus boat’ system will remain stationary with respect to water

a) in all cases

b) only when the man is stationary initially and finally

c) only if the man moves without acceleration on the boat

d) only if the man and the boat have equal masses

Answer: in all cases

Question: Statement 1 : When you lean behind over the hind legs of the chair, the chair falls back after a certain angle.
Statement 2 : Centre of mass lying outside the system makes the system unstable.

a) Statement -1 is true, Statement-2 is false

b) Statement -1 is true, Statement-2 is true; Statement -2 is not a correct explanation for Statement-1

c) Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1

d) Statement -1 is false, Statement-2 is true

Answer: Statement -1 is true, Statement-2 is false

Question: A system consists of three particles, each of mass m and located at (1, 1), (2, 2) and (3, 3). The co-ordinates of the centre of mass are

a) (2, 2)

b) (3, 3)

c) (6, 6)

d) (1, 1)

Answer: (2, 2)

Question: Two bodies of masses 2 kg and 4 kg are moving with velocities 2 m/s and 10 m/s respectively along same direction. Then the velocity of their centre of mass will be

a) 7.3 m/s

b) 6.4 m/s

c) 5.3 m/s

d) 8.1 m/s

Answer: 7.3 m/s

Question:

a)

b)

c)

d)

Answer:

Question:

a) 1/3

b) 1/2

c) 1/6

d) 1/4

Answer: 1/3

Question:  The centre of mass of three bodies each of mass 1 kg located at the points (0, 0), (3, 0) and (0, 4) in the XY plane is

a)

b)

c)

d)

Answer:

Question:  Two objects P and Q initially at rest move towards each other under mutual force of attraction. At the instant when the velocity of P is v and that of Q is 2v, the velocity of centre of mass of the system is

a) zero

b) 2v

c) 3v

d) v

Answer:  zero

Question:

a) 2a = b

b) a = 2b

c) a = b

d) 3a = 2b

Answer: 2a = b

Question: The position of centre of mass of a system of particles does not depend upon the

a) None of these

b) position of the particles

c) symmetry of the body

d) mass of particles

Answer:  None of these