Chapter 12 Vehicle Movement - FACTORS THAT AFFECT YOUR DRIVING IN: - 3 Major high conditions that require a speed adjustment - 4 components of total stopping distance - Natural Laws Inertia, friction, momentum, kinetic energy and gravity - Factors affecting steering - Natural Laws and their effect on the car
Lesson 1 Using Appropriate Speed Adjusting Speed to highway conditions Visibility Increased speed = lower ability to stop to avoid an accident in inclement weather Must have good visibility at intersections, driveways, and roadside areas Traction Rain, snow, or hail makes the road slippery Decreased traction = increased stopping distance 6 to 8 seconds in certain situations need to be added to the stopping distance Space Stopping distance should be less then your distance you can see ahead
Lesson 2 Stopping Distance What is total stopping distance? Distance it takes to stop any vehicle Human-perception distance Distance the car travels while you recognize a change or hazard Human-reaction distance Time it takes to physically react to what you see Vehicle-braking distance Time for vehicle mechanics to work once the brake is hit
Lesson 2: Total Stopping Distance Braking capability Type of braking system Brake pad material Brake alignment Vehicles tire pressure Tire tread and grip Vehicle weight Suspension system depends on: Coefficient of friction of road service Wind speed Slow of road Road s surface smoothness Braking technique applied by the driver
Stopping in snow and other low traction environments HTTPS://WWW.YOUTUBE.COM/WATCH?V=BZCEZ5G-CKC (START AT 2:42)
Lesson 3: Natural Laws and the Movement of Your Vehicle Natural Laws Forces in nature always at work Inertia Friction Momentum Kinetic Energy Gravity
Lesson 3: Natural Laws and the Movement of Your Vehicle Inertia 2 aspects Moving objects continue to move in a straight line until a force acts on them Objects at rest stay at rest unless a force is applied Braking quickly gives the illusion everything else is still moving wearing a seatbelt can reduce this sensation Secure all objects in the car to reduce risk of injuries from inertia
Lesson 3: Natural Laws and the Movement of Your Vehicle Friction Force between two objects that resists the objects from moving across each surface Traction Friction between your tires and the road Factors affecting traction Tire pressure Every tire has a certain level it should be inflated Tire condition Tires can bald (loose their grooves) over time and will wear in certain patterns need to rotate tires every so often think your sole on your shoe Legal Tread is 1/16 th of an inch doesn t mean it is completely safe Rain Smooth and can lower traction Hydroplaning Snow/Ice Reduce traction more than rain Any road is dangerous when covered with snow and/or ice https://www.youtube.com/watch?v=spaoedd3rgo
Lesson 3: Natural Laws and the Movement of Your Vehicle Momentum Quality of motion in a moving object, combination of weight and speed Greater speed = greater momentum Greater weight = greater momentum Kinetic Energy Gravity Energy of motion not the motion itself Accelerating/Braking Page 260 & 261 Force that pulls all objects toward the earth Going uphill will be harder because gravity is slowly pulling your car down Center of gravity The lower the center of gravity the more stable the car will be and harder it is to roll over
Lesson 4 Natural Laws and Steering/Braking Steering affects from natural laws Directional control Vehicles ability to hold a straight line or to continue a particular direction Steering around a curve Inertia tends to keep vehicle moving straight Feel a force pulling you wide on a curve centrifugal force Centrifugal force pushes the car opposite of the way you are turning Figure 12.3 Faster you go the more difficult it is for traction to overcome inertia Figure 12.4 Gravity and road contour Banked roads 1 area built higher then others (think nascar track) Crowned roads Higher in the center then the outside