Lesson 7 – Momentum & Collisions

Phase 3: Exam Mastery
Page 7 – Previous IIT / JEE Objective Questions

This page contains authentic IIT-JEE style objective questions inspired from previous years, with correct reasoning, elimination tricks, and exam tips.

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Q1. (IIT-JEE)

Two particles collide elastically in one dimension. Which of the following quantities is always conserved?

• A) Momentum only
• B) Kinetic energy only
• C) Momentum and kinetic energy
• D) Momentum, kinetic energy and velocity

✔ Correct Answer: C

Trick: Elastic collision = both momentum & KE conserved.

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Q2. (JEE Main)

A ball strikes a rigid wall and rebounds. The magnitude of impulse imparted to the ball depends on:

• A) Time of contact
• B) Change in velocity
• C) Mass of the wall
• D) Area of contact

✔ Correct Answer: B

Tip: Impulse = change in momentum, not time.

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Q3. (IIT-JEE Advanced)

A body at rest explodes into two fragments. Which of the following remains unchanged immediately after explosion?

• A) Total kinetic energy
• B) Momentum of each fragment
• C) Velocity of centre of mass
• D) Speed of fragments

✔ Correct Answer: C

Examiner Trap: KE changes, but COM velocity stays same.

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Q4. (JEE Main)

Two bodies stick together after collision. Which statement is correct?

• A) e = 1
• B) e = 0
• C) Momentum is not conserved
• D) Kinetic energy is conserved

✔ Correct Answer: B

Shortcut: Sticking together → perfectly inelastic.

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Q5. (IIT-JEE)

In a collision, momentum is conserved but kinetic energy decreases. This collision is:

• A) Elastic
• B) Perfectly elastic
• C) Inelastic
• D) Super elastic

✔ Correct Answer: C

Tip: KE loss ≠ momentum loss.

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🧠 Exam Strategy for Objective Questions

✔ Read options before solving fully
✔ Look for conservation law violations
✔ Eliminate impossible options first
✔ Avoid overthinking simple questions
✔ Trust physics, not intuition

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📌 What’s Next?

Next page will include:
✔ More Previous Year MCQs
✔ Multi-correct questions
✔ Assertion–Reason type
✔ Speed-solving tricks

👉 Next: Page 8 – Previous Papers (Advanced Level MCQs)