Topic 9: Law of Conservation of Momentum (Imp)

Q1. The law of conservation of momentum is valid when:
A) External force is maximum
B) External force is zero
C) Internal force is zero
D) Bodies are at rest

Answer: B


Q2. Momentum of a system remains constant if the system is:
A) Closed
B) Open
C) Isolated
D) Moving

Answer: C


Q3. Which of the following obeys the law of conservation of momentum?
A) Falling stone
B) Motion under gravity
C) Collision of two balls
D) Motion with friction

Answer: C


Q4. In the absence of external force, total momentum:
A) Increases
B) Decreases
C) Remains constant
D) Becomes zero

Answer: C


Q5. Recoil of a gun is explained by:
A) Newton’s first law
B) Newton’s second law
C) Newton’s third law
D) Conservation of momentum

Answer: D


Q6. Before and after interaction, total momentum of a system is:
A) Different
B) Zero
C) Same
D) Infinite

Answer: C


Q7. Which condition is necessary for conservation of momentum?
A) Constant velocity
B) Constant acceleration
C) No external force
D) Same mass

Answer: C


Q8. Explosion of a bomb is an example of:
A) Law of inertia
B) Newton’s second law
C) Conservation of energy
D) Conservation of momentum

Answer: D

Chapter 2: Laws of Motion

Topic 9: Law of Conservation of Momentum – Quick Revision

1. Statement

If no external force acts on a system, the total momentum of the system remains constant.

2. Condition

System must be isolated (no external force).

3. Formula

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

4. Key Points

• Total momentum before interaction = total momentum after interaction
• Valid only in absence of external force

5. Examples

• Recoil of a gun
• Collision of bodies
• Explosion of a bomb

Exam Focus (MHT-CET)

Numericals and MCQs are frequently asked on conservation of momentum in collisions and explosions.