Idaho Public Driver Education Natural Laws Affecting Vehicle Control

The natural force that pulls all things to earth GRAVITY The natural force that pulls all things to earth The center of gravity is where a body’s mass is ___________ Throw a ball into the air and it________ Gravity gives objects their ________

ENERGY 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 WEIGHT A vehicle’s energy of motion changes in proportion to the square of the change in speed To 40mph 20mph Takes FOUR times the distance to stop To 60mph 20mph Takes NINE times the distance to stop

EFFECT OF SPEED AND WEIGHT To stop a vehicle going 60mph would generate approximately enough heat to boil ½ gallon of water! ½ Gallon

INERTIA Inertia wants to keep these parked cars at rest. Inertia also wants to keep these moving cars moving.

INERTIA Why, when driving through this curve, does inertia create the sensation that you are being pulled to the outside of the curve? Because you are traveling in a straight line and inertia wants to keep you going in a straight line

MOMENTUM 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

MOMENTUM 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!

U think U can bench press an elephant? 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, ROLL, YAW Yaw Pitch Roll

FORCES OF IMPACT 1. Speed 2. Weight 3. Duration When two objects collide, 3 factors determine how much force there will be on impact 1. Speed 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 2. Weight 3. Duration

FRICTION The amount of friction between the surfaces depends on: 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 Types Friction creates TRACTION 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 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!

Traction Pies 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 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 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 the vehicle accelerates, brakes, or turns, the vehicle balance is changed As soon as motion occurs, weight transfer on the tires changes the size of the tire patches Going up or down a hill, or around a corner, or BOTH at the same time, really puts physics into play!

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

THE ULTIMATE VEHICLE OVER LOAD

Maximizing 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 CRASH 1. Car hits object

2. Head hits windshield Body into steering wheel, dashboard, other passengers, etc.

3. Brain hits skull 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 Priority! Idaho Child Safety Seat Laws 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 Head Restraints Proper adjustment to avoid neck injury Seat position

Occupant Protection Adjustable Head Restraint Shoulder-Belt Mount Air Bag Gases Vent Opening Crash Sensors

Adjusting Belts for Proper Fit 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

AIR BAGS Air Bags in Dash or Steering Wheel 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

Like Most Victims, Julie Knew Her Killer… Wear Your Seatbelt! In the front AND back!