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Gravity  Gravity (Natural Law)– force that pulls all things to earth  Driving Up Hill – acts against gravity  Naturally loose speed  Must accelerate.

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Presentation on theme: "Gravity  Gravity (Natural Law)– force that pulls all things to earth  Driving Up Hill – acts against gravity  Naturally loose speed  Must accelerate."— Presentation transcript:

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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  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 (x 2 )  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  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  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 1/16 th 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  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 (x 2 )  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


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