ACTIVE PHYSICS 3.4

Newton’s Second Law: Rear End Collisions

JANUARY 25, 2012HOMEWORK: 3.4 PTG, P 299 #1-7 DUE FRIDAY

Learning Objective Apply Newton’s 1st and 2nd

Law to automobile crashes Process Skill:

Rewrite/Follow step-by-step procedures

Success Criteria Describe the causes of

whiplash Provide examples of

Newton’s 1st and 2nd Laws in automobile crashes

Analyze safety devices in preventing whiplash

Do Now Copy LO and SC on

new left side page! WDYS/WDYT p 292

Agenda Do Now: Lab with more clay

crash dummies! Summary

Rewrite procedures in your own words. Be sure to leave spaces to record data

and observations OK with LePera before going into lab

REAR-END COLLISIONSMaterials Needed

Ramp2 Crash cartsManila FolderRing standClay passengersSeat papersScissorsMeter StickMasses

EXIT TICKET What type of seat causes less

whiplash? Explain why in terms of Newton’s 1st and 2nd Law.

Learning Objective Apply Newton’s 1st and 2nd

Law to automobile crashes Process Skill:

Rewrite/Follow step-by-step procedures

Success Criteria Describe the causes of

whiplash Provide examples of

Newton’s 1st and 2nd Laws in automobile crashes

Analyze safety devices in preventing whiplash

Do Now: Why is it important to

align the headrest appropriately to the height of the driver?

Agenda Do Now Physics Talk Summary

PHYSICS TALK 3.4 What is Newton’s

Second Law?

If a body is acted on by an unbalanced force, it will accelerate in the direction of the unbalanced force.

The acceleration will be larger for smaller masses.

The acceleration can be an increase in speed, decrease in speed, or change in direction.

F=ma

REAR-END COLLISION What is whiplash?

Why does it hurt?

A serious injury often caused by a rear-end collision.

The back of the seat, pushes the torso forward, leaving the head behind. This strains the neck and damages the alignment in the spine. The neck then snaps forward. Ouch!

Act out

NEWTON’S SECOND LAW Important note

about Newton’s second law

All accelerations are caused by unbalanced, outside forces

It does not say that all forces cause acceleration, only unbalanced ones.

How does Newton’s Second law apply to holding a book?

The force of your hand and the force of gravity are opposite forces acting on the same object, so the forces cancel out = no net force

How does Newton’s Second Law apply to a car traveling at a constant speed?

Since there is no acceleration, there is no net force. This means the forces are balanced.

The forces of the engine on the tires and road moving the car forward must be equal and opposite of the air pushing back on the car

ESSENTIAL QUESTIONS: Pg. 298 What does it mean? How do you know? Why should you care?

EXIT TICKET How does Newton’s Second Law apply

to rear-end collisions and whiplash?