Idaho Public Driver Education Idaho Public Driver Education

Natural Laws Affecting Vehicle

Control

GRAVITYGRAVITY

The natural force that pulls all things to earth

Throw a ball into the air and it________

Gravity gives objects their ________

The center of gravity is where a body’s mass is ___________

ENERGY OF MOTIONENERGY OF MOTION

The white truck and the dump truck are going the same speed.

Which vehicle has more energy of motion?

Why?

EFFECT OF SPEED AND WEIGHTEFFECT OF SPEED AND WEIGHTA vehicle’s energy of motion changes in

proportion to the square of the change in speed

Takes FOUR times the distance to stop

20mph

To 40mph20mph

To 60mph

Takes NINE times the distance to stop

EFFECT OF SPEED AND WEIGHTEFFECT OF SPEED AND WEIGHT

To stop a vehicle going 60mph would generate approximately enough heat to boil ½ gallon of water!

½ Gallon

INERTIAINERTIA

Inertia wants to keep these parked cars at rest.

• Inertia also wants to keep these moving cars moving.

Why, when driving through this curve, does inertia create the sensation that you are being pulled to the outside of the curve?

INERTIAINERTIA

Because you are traveling in a straight line and inertia wants to keep you going in a straight line

MOMENTUMMOMENTUM

• Momentum is inertia in motion

• Momentum is the product of speed and weight

A small truck filled with potatoes traveling at 20mph has more momentum that a 3,000 lb car traveling at the same speed

As momentum increases so does the potential for lots of damage in a collision

MOMENTUMMOMENTUM

A 50 lb passenger traveling in a vehicle going 30mph will have momentum.

No matter how strong that passenger may be, he will not be strong enough to stop the body’s momentum when the vehicle comes to an abrupt stop during a crash!

Some say, “I can brace myself in a wreck”, or “I’m strong enough to hold onto the steering

wheel”.

U think U can bench press an elephant?

Pitch

PITCH, ROLL, YAWPITCH, ROLL, YAW

Yaw

Roll

FORCES OF IMPACTFORCES OF IMPACT

When two objects collide, 3 factors determine how much force there will be on impact

1. Speed

2. Weight

3. Duration

When a collision stops a vehicle in a very short time the impact will be greater than if it took a longer time to stop

FRICTIONFRICTION

Friction is the force when two surfaces move against each other and one surface resists the other

The amount of friction between the surfaces depends on:

• What the surface is made of

• What is on the surface

• How rough or smooth it is

• How much force is pushing the two surfaces together

FRICTION: 4 TypesFRICTION: 4 Types

1. Static: The holding force between 2 surfaces

2. Sliding: Friction that slows down a sliding object

3. Rolling: Friction between the ground and tire/wheel

4. Internal: Friction that occurs from resistance to motion within elastic objects

Friction creates TRACTION

TIRES AND TRACTIONTIRES AND TRACTION

Only four small areas underneath each tire holds the vehicle on the road!

When the car is not moving, it’s got GREAT (static) traction!

Consumers of Traction

Acceleration Force

Braking Force

Turning Force

Traction PiesTraction Pies

Large Steering and Braking Forces Exceed Traction Limits

Large Steering Force Large Braking Force

In a hard braking situation, most of the traction is needed for braking

Add hard steering will result in loss of control

FORCE EFFECT ON OCCUPANTSFORCE EFFECT ON OCCUPANTS

As the car enters a turn, inertial wants to keep the vehicle and occupants going straight

The seat position and seat belts hold the passengers in place through the curve

MAINTAINING VEHICLE BALANCEMAINTAINING VEHICLE BALANCE

The design balance for a vehicle is only reached when the vehicle is not moving, or is moving in a straight line at a constant speed

As soon as motion occurs, weight transfer on the tires changes the size of the tire patches

As soon as the vehicle accelerates, brakes, or turns, the vehicle balance is changed

Going up or down a hill, or around a corner, or BOTH at the same time, really puts physics into play!

MAXIMUM VEHICLE LOADMAXIMUM VEHICLE LOAD

Load capacity includes the combined weight of people and Load capacity includes the combined weight of people and cargo that the vehicle is designed to safely handlecargo that the vehicle is designed to safely handle

THE ULTIMATE VEHICLE OVER LOADTHE ULTIMATE VEHICLE OVER LOAD

Maximizing Traction and ControlMaximizing Traction and Control

Properly inflated tires not only increase traction, they improve gas mileage and save you money!

Tires with plenty of tread help maintain traction!

A good suspension system helps keep the tires on the road, maximizing traction!

THE THREE COLLISIONS in a THE THREE COLLISIONS in a

CRASHCRASH

Body into steering wheel, dashboard, other passengers, etc.

There’s no airbag inside the skull! If the person lives, the result can be severe brain damage.

Protecting your Passengers Should be Your First Protecting your Passengers Should be Your First Priority!Priority!

– Rear-facing infant seat – First year of life

– Forward-facing infant seat – up to 40 lbs.

– 40 lbs. to age 7 - booster seat.

– Age 7 – seat belt

–Proper adjustment to avoid neck injury

–Seat position

Idaho Child Safety Seat Laws

Head Restraints

Adjustable

Shoulder-Belt Mount

Head RestraintAir Bag

Crash Sensors

Gases Vent Opening

Occupant ProtectionOccupant Protection

Lap belt

• low across hips

• snug across hips

• avoids internal injuries

Shoulder belt

• over collar bone and chest

• avoids shoulder dislocation

• avoids rib cage damage

Adjusting Belts for Proper FitAdjusting Belts for Proper Fit

AIR BAGSAIR BAGS

No passenger under 12 years of age in front seat

Protects against head and chest injuries

Speed of inflation is critical Driver should adjust seat for

minimum 10 inch clearance between chest and steering wheel

Hand position on wheel should be 9 and 3 or lower.

Aim steering wheel at chest not face

Air Bags in Dash or Steering Wheel

Like Most Victims, Julie Knew Her Killer…

In the front AND back!