LESSON–3 : MOTION IN A PLANE

ADDITIONAL MATERIALS – 9 (PART–4)
IIT PYQs – METHOD OPTIMIZATION & SOLVING FLOW

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🔹 PYQ–29 (JEE ADVANCED – METHOD REJECTION)

Question:
A projectile is thrown with speed u at an angle θ. Find its speed just before hitting the ground.

Correct Thinking:

• Do NOT use time equations
• Do NOT resolve components
• Use Energy Conservation

Solution:

Initial KE = Final KE (same height)
⇒ Speed before landing = u

Why this works:

Height difference = 0 → potential energy change = 0

Topper Trick:

Same level → same speed (immediate answer).

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🔹 PYQ–30 (JEE MAIN – DATA ELIMINATION)

Question:
A body is projected horizontally from a tower of height h with speed v. Find the time of fall.

Correct Approach:

• Ignore horizontal speed completely
• Consider only vertical free fall

Solution:

h = ½gt²
t = √(2h / g)

Trap Avoidance:

Horizontal velocity is given only to confuse.

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🔹 PYQ–31 (JEE ADVANCED – METHOD COMPARISON)

Question:
Find the speed of a projectile at a point where it makes angle φ with the horizontal.

Best Method:

• Use component relation: tanφ = v_y / v_x
• Use energy for magnitude

Key Insight:

Direction info → use components
Magnitude info → use energy

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🔹 PYQ–32 (JEE ADVANCED – RANGE WITHOUT FORMULA)

Question:
Two projectiles are fired with the same speed. One at 35° and the other at 55°. Which travels farther?

Logic:

• 35° + 55° = 90°
• Complementary angles

Answer:

Both travel the same distance.

Shortcut:

Angles adding to 90° → equal range.

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🔹 PYQ–33 (JEE MAIN – RELATIVE VELOCITY FLOW)

Question:
Two particles move with velocities v₁ and v₂ at angle θ. Find relative speed.

Correct Procedure:

1. Draw velocity triangle
2. Apply cosine rule

Answer:

Relative speed = √(v₁² + v₂² − 2v₁v₂cosθ)

Method Selection Rule:

If angle ≠ 90° → use cosine rule.

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🔹 PYQ–34 (JEE ADVANCED – TIME SYMMETRY)

Question:
Compare time taken by projectile to rise to maximum height and time to fall back to the same level.

Answer:

Times are equal.

Concept:

Projectile motion is symmetric about highest point.

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🔹 PYQ–35 (JEE ADVANCED – ZERO MISCONCEPTION)

Question:
At the highest point of projectile motion, which physical quantities are zero?

Correct Analysis:

• Vertical velocity = 0 ✔
• Horizontal velocity ≠ 0 ✖
• Acceleration ≠ 0 ✖
• Speed ≠ 0 ✖

Golden Rule:

Only one component becomes zero, never the acceleration.

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🔹 PYQ–36 (JEE MAIN – VECTOR PATTERN MEMORY)

Question:
Find the angle between vectors (a, a) and (a, −a).

Solution:

Dot product = a² − a² = 0
Angle = 90°

Memory Pattern:

(x, y) ⟂ (x, −y)

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🔹 PYQ–37 (JEE ADVANCED – METHOD PRIORITY TEST)

Question:
Which method is fastest to find speed of projectile at a given height?

Answer:

Energy conservation method.

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🧠 FINAL IIT DECISION TREE (PART–4)

1. If height or speed at height → Energy method
2. If time → Vertical motion only
3. If range → Symmetry or sin2θ
4. If relative motion → Vector geometry
5. If direction → Components
6. Ignore unnecessary data immediately

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✅ ADDITIONAL MATERIALS – 9 (PART–4) COMPLETED
(METHOD OPTIMIZATION & TOPPER THINKING)

Intermediate Physics Complete Notes – IIT JEE & Board Exams

This page contains complete Intermediate Physics notes along with IIT JEE materials, previous year questions, solved problems, diagrams, and exam strategies.

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📘 Lesson 1: Units and Measurements

• Complete Notes
• Important Questions

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📘 Lesson 2: Motion in a Straight Line

• Complete Notes
• Important Questions
• IIT JEE Material
• IIT JEE PYQs & Strategy
• Diagrams

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📘 Lesson 3: Motion in a Plane

• Part 1
• Part 2
• Part 3
• Part 4
• Part 5
• Part 6
• Part 7
• Part 8
• Part 9
• Part 10
• Part 11
• Part 12
• Part 13
• Part 14
• Part 15
• Part 16
• Part 17

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 This page is updated regularly with new lessons.