Impulse Formula Explained with Cricket Ball Example for NEET

 Change in Momentum and Impulse Numerical Solution Step by Step

Example 4.4 – Impulse Imparted to a Cricket Ball (Easy NEET Notes)

Impulse imparted to a cricket ball when its direction reverses after being hit by a batsman.

- Dr.Sanjaykumar pawar 

Question

Example 4.4 A batsman hits back a ball

straight in the direction of the bowler without

changing its initial speed of 12 m s–1

.

If the mass of the ball is 0.15 kg, determine

the impulse imparted to the ball. (Assume

linear motion of the ball)

A batsman hits back a ball straight towards the bowler without changing its speed.

Given:

• Mass of ball, m = 0.15 kg
• Initial speed, u = 12 m/s
• Final speed, v = 12 m/s
• Direction changes completely after being hit.

Find the impulse imparted to the ball.

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Step 1: Understand the Situation

Before hitting:

Bowler → Ball → Batsman

After hitting:

Bowler ← Ball ← Batsman

The ball returns in the opposite direction.

Important Concept

• Speed remains the same.
• Direction changes.
• Velocity changes because velocity depends on both speed and direction.

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Step 2: Choose Positive Direction

Take the direction from batsman to bowler as positive (+).

Then:

• Initial velocity = −12 m/s (because ball is moving towards batsman)

• Final velocity = +12 m/s (because ball is moving towards bowler)

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Step 3: Write Initial Momentum

Momentum = Mass × Velocity

Initial momentum:

pᵢ = m × u

pᵢ = 0.15 × (−12)

pᵢ = −1.8 kg m/s

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Step 4: Write Final Momentum

Final momentum:

pᶠ = m × v

pᶠ = 0.15 × (+12)

pᶠ = +1.8 kg m/s

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Step 5: Calculate Change in Momentum

Change in momentum:

Δp = pᶠ − pᵢ

Δp = (+1.8) − (−1.8)

Δp = 1.8 + 1.8

Δp = 3.6 kg m/s

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Step 6: Use Impulse Formula

Impulse = Change in Momentum

Therefore,

Impulse = 3.6 N·s

(1 kg m/s = 1 N·s)

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Final Answer

Impulse imparted to the ball = 3.6 N·s

Direction: From batsman towards bowler.

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Quick NEET Shortcut

When an object rebounds with the same speed:

Initial momentum = −mv

Final momentum = +mv

Change in momentum:

Δp = (+mv) − (−mv)

Δp = 2mv

For this question:

Δp = 2 × 0.15 × 12

Δp = 3.6 N·s

✅ Answer = 3.6 N·s (towards the bowler)

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NEET Exam Tip

Whenever a ball rebounds (comes back):

✔ Direction changes

✔ Use opposite signs for velocities

✔ Momentum change becomes large because:

Change in momentum = Final momentum − Initial momentum

and subtracting a negative number becomes addition.

INTERNAL LINK

• What is Momentum? Definition, Formula and Examples • Impulse and Momentum Relationship Explained • Newton's First Law of Motion Notes • Newton's Second Law of Motion Explained • Newton's Third Law of Motion Easy Notes • Law of Conservation of Momentum • Force and Acceleration Numericals • Important NEET Physics Formulas • Class 11 Mechanics Complete Notes • NEET Physics Chapter-Wise Questions