1. Natural Laws & Car Control
Chapter 5

2. Gravity Gravity (Natural Law)– force that pulls all things to earth
Driving Up Hill – acts against gravity
Naturally loose speed
Must accelerate to maintain speed
Braking distance shortened
Down Hill
Naturally gain speed
It will take longer to stop
Braking distance will be longer
Steeper the incline – longer the stopping distance

3. Gravity Center of Gravity Kinetic Energy – energy in motion
Point around which an objects weight is evenly distributed
Automobile makers attempt to lower car’s center of gravity so it handles better
Higher the center of gravity = more unstable (see pg 92)
Kinetic Energy – energy in motion
Object moves it picks up energy
Faster = More energy
More Weight = More energy of motion (kinetic energy)

4. Energy of Motion As speed & weight of a vehicle increases…
More speed = longer distance to stop
Speed doubles = 4x more stopping distance (x2)
Speed triples = ___ more stopping distance
Speed quadruples = _____ more stopping distance
More weight = longer distance to stop
Weight doubles = Stopping distance doubles
See picture pg 93

5. Friction & Traction
Friction – force that keeps each tire from sliding on the road
Traction – friction created by tires
Makes it possible for tires to grip the road
Traction allows the car to move, change speed, direction, etc.
Tread –created by grooves - grooved surface on tire
Wet Road Conditions – allows water to flow through the grooves away from the tire
Hydroplaning - car floats on water – looses traction
More tread on the road = more gripping = more control
So… Tires play the most important role in maintaining control

6. Tires Bald Tires Tire Inflation
Little tread = little gripping = little control
Dangerous especially on icy or wet roads
Increase risk of blowouts - rapid loss of air pressure
Tire Inflation
Each tire works best at certain air pressures
Too much or too little changes the amount of tread on the road
Remember: More tread on the road = more control
Also: Correct tire pressure = Better gas mileage
Tires roll easier at correct pressure

7. Tires & Inflation
Under Inflation – only outside edge of tire provides traction
Outside edges wear first
Will fail quicker
Over Inflation – only the center of the tire provides traction
Center will wear out first
Temperature
Colder = lower tire pressure
Hotter = increase tire pressure
Check Tire pressure regularly before driving

8. Traction Split Traction 2 Things Needed for Ideal Traction
When braking & turning or braking & accelerating
Some traction is used for braking or accelerating
Some traction is used for turning
2 Things Needed for Ideal Traction
#1. Good Vehicle Condition
Tires, shock absorbers, steering system
Worn shocks will cause car to bounce off the road
Tire Treads – must have at least 1/16th of an inch
Penny Test – shouldn’t be able to see all of Lincoln’s head
#2. Good Road Conditions (Concern = Ice!)

9. Curves
Energy of Motion (Kinetic Energy) will try to make you go straight around a curve
Faster = greater force to go straight
Vehicle Control in a Curve (4 factors)
#1 Speed
Higher speed = less control
Lower speed = more control
Best Practice: Lower speed before entering a curve
#2 Sharpness of Curves
Sharper curve = more needed traction
Best Practice: Sharper curve = slower speed

10. Curves Vehicle Control in a Curve (4 factors continued)
#3 Banked Curves – higher on the outside vs inside
Helps to reduce vehicle’s tendency to move to the outside
#4 Load of the Vehicle
Higher load = more kinetic energy
Best Practice: Higher load , slower around curves
Vehicles of Different Sizes & Power Handle Differently
Smaller vehicle = generally stop & accelerate quicker

11. Stopping Distance Total Stopping Distance
Distance the Car travels while you make a stop
Must do 3 things to stop
#1 Perceive the hazard
#2 React
#3 Brake
Perception Time
Time it takes to Identify, predict & decide
Varies based on
Visibility, the hazard & driver abilities
Perception Distance
Distance vehicle travels during this time

12. Stopping Distance Reaction Time Braking Distance
Length of time it takes to execute action
Average driver’s reaction time = ¾ of a second
Reaction Distance
Distance vehicle travels while you react
Braking Distance
Distance vehicle travels from the time you apply the brakes until the vehicle stops
Remember: Faster = longer stopping distance (x2)
Example: 40 mph will have a 4x longer braking distance than 20mph

13. Stopping Distance
Also see page 98

14. Estimating Stopping Distance
4 Second Rule – used to estimate stopping distance
Pick an object on the road ahead where you think you can stop
Count 4 seconds
Check vehicle position
Note: It will take you 300’ (football field) to stop going 65 mph
Factors That Affect Braking
Speed – faster = longer braking distance
Vehicle Condition -worn tires/shocks = longer braking distance

15. Factors Affect Braking
Roadway Surface – rain/snow/gravel = longer BD
Driver Ability – distracted or impaired = longer BD
ABS - Can better stop your vehicle while turning
Hills – Uphill = shorter / Downhill = longer
Loads – Heavy Loads = longer BD

16. Controlling Force of Impact
Force of Impact – force generated when one moving object hits another
3 Factors Determine “Force of Impact”
Speed – increase or decrease in speed squares the force of the impact
Weight of Vehicle – heavy vehicle = greater force of impact
Distance between Impact and stopping – Hit something that doesn’t “give” = greater force of impact

17. Seat Belts & Air Bags 3 Collisions Occur in a Crash
Vehicle hits object
Occupants hit the inside of the vehicle
Body organs (brain, heart, liver) hit skeleton
Restraint Devices - holds occupant in place
Passive Restraint – works automatically – occupant doesn’t have to do anything (Ex. Airbag)
Active Restraint – device you have to engage (Ex. Seatbelt)
Wear it properly

18. Air Bags Deploy at 200 mph Designed to work with seat belts
Most air bags are only effective with front collisions
Seat Belts help in side/ rollover etc.
Keep hands at 9 & 3
Sit Back – chest should be 10 “ away
Children in child seats and children under 12 must sit in back seat
Advancements
Sensors for weight and position in seat
Switch to turn off

19. Supplemental Devices Front or Rear End crushes on impact
Energy absorbing bumpers
Side door beams
Reinforced Windshields
Energy absorbing steering columns
Padded Dash
Child Safety Seats – back seat – required in all states
Head Restraints