Chapter 3, Section 6Conservation of Momentum

Date: 2/6/12HW: 3.6 PTG #1-16, pg. 319-320

Learning Objective:• Describe conservation

of momentum in collisions

Success Criteria:• Calculate momentum in

a system• Define conservation of

momentum in words and equations

Do Now:• Copy LO and SC on new

left side page• WDYS/WDYT pg. 310

Agenda:• Do Now• PhET/Investigate• Physics Talk• PTG• Summary/Quiz

Investigate: Collision PhET

collision-lab_en.jar

Mass of Object 1 (kg)

Mass of Object 2 (kg)

Velocity of Object 1 before collision (m/s)

Velocity of Object 2 before collision (m/s)

Mass of combined objects after collision (kg)

Velocity of combined objects after collision (m/s)

1.0 1.0 0.0 2.0

2.0 1.0 0.0 3.0

1.0 2.0 0.0 3.0

Momentump=mv

Before Collision After Collision

Momentum of Object 1 kg*(m/s)

Momentum of Object 2 kg*(m/s)

Momentum of Combined objects 1 and 2 kg*(m/s)

Physics Talk 3.6 What is the

Conservation of Momentum?

The total momentum before a collision, is equal to the total momentum after the collision if no external forces act on the system.

What is the equation for momentum?

What is the equation for conservation of momentum?

p=mv• p=momentum

[kg*(m/s)]• m=mass (kg)• v=velocity (m/s)

Why is this equation written like this?

You added the masses after the collision because they stuck together

Pool ball example Single cue ball hits a rack of 15 balls…momentum is conserved!

Total momentum before is equal to the total momentum after the collision

The balls move in new directions with new speeds, but the momentum stays the same!

Why is conservation of momentum important?

Used to investigate traffic accidents

If you know masses and velocities of two objects, you can predict the velocity after the collision…you can predict the future!

2/8, 2012HW: Grade Report Signed

Learning Objective:• Describe conservation

of momentum in collisions

Success Criteria:• Calculate momentum in

a system• Define conservation of

momentum in words and equations

Do Now:• 10 minutes to complete

packet

Agenda:• Do Now• PhET/Investigate• Physics Talk• PTG• Summary/Quiz

Practice Problems PTG pg. 319 #1-16

Essential Questions LO and SC

Reflection Answer essential

questions pg. 318

Quiz!