Chapter 9. Impulse and Momentum - Northern Highlands ... · Chapter 9. Impulse and Momentum ......

Chapter 9. Impulse and MomentumChapter 9. Impulse and Momentum Explosions and collisions obey some surprisingly simple laws that make problem solving easier when comparing the situation before and after an interaction.Chapter Goal: To introduce the ideas of impulse and momentum and to learn a new problem-solving strategy based on conservation laws.

Topics:• Momentum and Impulse • Solving Impulse and Momentum Problems • Conservation of Momentum • Inelastic Collisions • Explosions • Momentum in Two Dimensions

Chapter 9. Impulse and Momentum Chapter 9. Impulse and Momentum

Chapter 9. Reading QuizzesChapter 9. Reading Quizzes

A. a force that is applied at a random time.

B. a force that is applied very suddenly.C. the area under the force curve in a

force-versus-time graph.D. the time interval that a force lasts.

Impulse is

A. a force that is applied at a random time.

B. a force that is applied very suddenly.C. the area under the force curve in a

force-versus-time graph.D. the time interval that a force lasts.

Impulse is

The total momentum of a system is conserved

A. always.B. if the system is isolated.C. if the forces are conservative.D. never; it’s just an approximation.

The total momentum of a system is conserved

A. always.B. if the system is isolated.C. if the forces are conservative.D. never; it’s just an approximation.

In an inelastic collision,

A. impulse is conserved.B. momentum is conserved.C. force is conserved.D. energy is conserved.E. elasticity is conserved.

In an inelastic collision,

A. impulse is conserved.B. momentum is conserved.C. force is conserved.D. energy is conserved.E. elasticity is conserved.

Chapter 9. Basic Content and ExamplesChapter 9. Basic Content and Examples

Impulse and MomentumImpulse and MomentumMomentum is the product of a particle’s mass and velocity, has units of kg m/s, and is given by

The impulse upon a particle is defined as

Impulse has units of N s, but you should be able to show that N s are equivalent to kg m/s. The impulse-momentum theorem is

Tactics: Drawing a before-and-after pictorial Tactics: Drawing a before-and-after pictorial representationrepresentation

EXAMPLE 9.2 A bouncing ball

QUESTION:

Conservation of Momentum

Stated mathematically, the law of conservation of momentum for an isolated system is

The total momentum after an interaction is equal to the total momentum before the interaction.

EXAMPLE 9.3 Two balls shot from a tube

QUESTION:

Problem-Solving Strategy: Conservation of Momentum

Conservation of Momentum Depends on the System

EXAMPLE 9.5 An inelastic glider collision

QUESTION:

EXAMPLE 9.9 Momentum in a 2D car crash

Chapter 9. Summary Slides

General Principles

Important Concepts

Applications

Chapter 9. Clicker Questions

The cart’s change of momentum is

A. 30 kg m/s.B. 10 kg m/s.C.–10 kg m/s.D.–20 kg m/s.E.–30 kg m/s.

The cart’s change of momentum is

A. 30 kg m/s.B. 10 kg m/s.C.–10 kg m/s.D.–20 kg m/s.E.–30 kg m/s.

A. They exert equal impulses because they have equal momenta.

B. The clay ball exerts a larger impulse because it sticks.

C. Neither exerts an impulse on the wall because the wall doesn’t move.

D. The rubber ball exerts a larger impulse because it bounces.

A 10 g rubber ball and a 10 g clay ball are thrown at a wall with equal speeds. The rubber ball bounces, the clay ball sticks. Which ball exerts a larger impulse on the wall?

A. They exert equal impulses because they have equal momenta.

B. The clay ball exerts a larger impulse because it sticks.

C. Neither exerts an impulse on the wall because the wall doesn’t move.

D. The rubber ball exerts a larger impulse because it bounces.

A 10 g rubber ball and a 10 g clay ball are thrown at a wall with equal speeds. The rubber ball bounces, the clay ball sticks. Which ball exerts a larger impulse on the wall?

Objects A and C are made of different materials, with different “springiness,” but they have the same mass and are initially at rest. When ball B collides with object A, the ball ends up at rest. When ball B is thrown with the same speed and collides with object C, the ball rebounds to the left. Compare the velocities of A and C after the collisions. Is vA greater than, equal to, or less than vC?

A. vA > vC B. vA < vC

C. vA = vC

Objects A and C are made of different materials, with different “springiness,” but they have the same mass and are initially at rest. When ball B collides with object A, the ball ends up at rest. When ball B is thrown with the same speed and collides with object C, the ball rebounds to the left. Compare the velocities of A and C after the collisions. Is vA greater than, equal to, or less than vC?

A. vA > vC B. vA < vC

C. vA = vC

A. vf = v2. B. vf is less than v2.C. vf is greater than v2, but less than v1. D. vf = v1. E. vf is greater than v1.

The two particles are both moving to the right. Particle 1 catches up with particle 2 and collides with it. The particles stick together and continue on with velocity vf. Which of these statements is true?

A. vf = v2. B. vf is less than v2.C. vf is greater than v2, but less than v1. D. vf = v1. E. vf is greater than v1.

The two particles are both moving to the right. Particle 1 catches up with particle 2 and collides with it. The particles stick together and continue on with velocity vf. Which of these statements is true?

An explosion in a rigid pipe shoots out three pieces. A 6 g piece comes out the right end. A 4 g piece comes out the left end with twice the speed of the 6 g piece. From which end does the third piece emerge?

A. Right endB. Left end

An explosion in a rigid pipe shoots out three pieces. A 6 g piece comes out the right end. A 4 g piece comes out the left end with twice the speed of the 6 g piece. From which end does the third piece emerge?

A. Right endB. Left end

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