1. Natural Laws and Car Control
Chapter 5
Natural Laws and Car Control

2. Gravity and Energy of Motion
How does gravity effect our cars while driving?
Uphill?
Downhill?
Braking Distance?
Center of Gravity
What might happen to a vehicle with a high center of gravity in a curve or on a hill?
Energy of Motion (Kinetic Energy)
Dependent on Weight and Speed
What happens to energy of motion if you double the vehicle’s weight?
Doubles energy of motion, which doubles stopping distance.
What happens if you double the vehicle’s speed instead?
Quadruples the energy of motion, which requires 4x’s the stopping distance.
Gravity = the force that pulls everything down to earth.
Uphill = gravity pulls us down requiring us to accelerate to get to the top of the hill. Shortens braking distance.
Downhill = gravity speeds us up requiring us to reduce speed/brake to maintain speed limit. Extends braking distance.
Center of gravity = the point around which an object’s weight is evenly distributed.
Energy of motion = the energy an object has because it is moving (Kinetic Energy)
Double weight = double KE – directly proportional to change.
Double speed = 4x’s KE – proportional to the square of the change in speed.

3. Friction and Traction Friction Traction
What systems in our cars use friction, besides tires?
Traction
How would traction be affected in the following situations?
Gravel Road?
Fresh Snow?
Packed Snow?
Dry Pavement?
Wet Pavement?
Over-inflated Tires?
Under-inflated Tires?
Bumpy Road?
Friction = the force that keeps each tire from sliding on the road.
Brakes use friction to stop vehicle.
Traction = the friction created by the tire and the roadway surface. Makes it possible for your vehicle to grip the road, change speed, and change direction.

4. Reduced Traction What would ideal conditions be for the best traction?
What situations might cause reduced traction?
Vehicle related situations?
Roadway situations?
How can you check your traction?
Check rear zones to make sure no traffic is near.
Brake gently to see how vehicle responds.
If vehicle doesn’t slow or ABS kick in, traction is poor so reduce you speed.
Best traction would be with properly inflated, well-maintained tires on a smooth, paved, level, clean roadway.

5. Curves What factors affect your vehicles control in a curve?
Speed
Sharpness of Curve
Banked Curve
Load
What is your best choice when dealing with a curve?
SLOW DOWN!!!
Speed = reduce speed before entering a curve/turn to avoid skidding in curve, accelerate as you leave the curve/turn.
Sharpness of curve – the sharper the curve the more traction required to hold you in place, reduce speed to help yourself maintain control.
Banked curve – the outside part of the curve is higher than the inside part of the curve, helps overcome your vehicles tendency to move to outside part of the curve.
Load – may change center of gravity causing your vehicle to become less stable

6. Stopping Distance Total Stopping Distance Perception Time and Distance
What might affect perception time?
Reaction Time and Distance
What is an average human’s reaction time?
Braking Time and Distance
Total stopping dist. = the dist. your car travels while you make a stop.
Perception Time and Dist. = the amount of time/distance it takes you to I, P, D to slow for a hazard.
Affect perception time = visibility, hazard itself, your abilities
Reaction time and dist – length of time/distance it takes you to execute your action once you’ve recognized a hazard
Avg. time = ¾ of a second.
Braking Time and Dist – amount of time/distance from when brakes are first applied to when you come to a complete stop.

7. Factors That Affect Braking Distance
Speed
Vehicle Condition
Roadway Surface
Driver Ability
Antilock Braking System (ABS)
Hills
Loads

8. Force of Impact 3 Factors determine how hard you hit something! Speed
Weight
Distance Between Impact and Stopping
FOI = the force with which a moving object hits another object.
Speed = double speed – 4x’s FOI
Weight = double weight – double FOI
Distance between impact and stop – shorter the distance the greater the FOI

9. For your quiz You should be able to:
List the four factors that affect your vehicles control in a curve
Explain how center of gravity affects the handling of your car
List and explain the three parts of total stopping distance
List the factors that affect your braking distance
List and explain the three factors involved in Force of Impact
Explain how gravity affects your vehicle on a roadway