Natural Laws and Car Control

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Chapter 5
Natural Laws and Car Control
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Chapter 5 Overview

• Chapter 5 presents natural laws that apply to
  driving. You will learn about gravity, energy of
  motion, friction, traction, the parts of total
  stopping distance, and how to estimate stopping
  distance at different speeds. The force of
  impact in a collision and the benefits of
  restraint devices are discussed.

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5.1 Gravity and Energy of Motion

• This section focuses on the natural laws of
  gravity and energy of motion and how they affect
  the way vehicles perform. The effects of weight
  and speed are also presented.
• Following this section, I will be able to
• 1. Explain how gravity affects your car.
• 2. Describe the factors that affect energy in
  motion.

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5.1 Vocabulary

• Following this section, I will be able to define
  the following
• 1. center of gravity
• 2. energy of motion
• 3. gravity

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Gravity

• The force that pulls all things back to earth.
• What happens when driving up and down hills?
• Center of gravity- (See pictures on p. 92)
• How does raising a vehicles center of gravity
  affect its stability?
• How does putting oversized tires on a vehicle
  affect its stability?

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Energy in Motion

• Kinetic energy or energy of motion is affected by
  speed and weight.
• Faster speed gives you more kinetic energy.
• Increased weight gives you more kinetic energy.
• When weight is doubled the energy of motion is
  doubled and needs twice as much distance to stop.

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Energy in Motion

• The energy of motion will change in proportion to
  the square of its change in speed.
• When the trucks speed doubles, it needs four
  times the distance to stop. If your speed
  triples, you need nine times the distance to
  stop.
• When you cut your speed in half, you cut your
  energy in motion by four times.

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Review

• 1. How does the force of gravity affect your car
  going downhill?
• 2. What factors affect energy of motion?

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5.2 Friction and Traction

• This section focuses on the natural laws of
  friction and traction and how they affect the way
  vehicles perform. The effects of improperly
  inflated tires also are presented.
• Following this section, I will be able to
• Explain how traction controls your car.
• List three things that can reduce traction.
• Describe how you can check traction while
  driving.
• List factors that affect your car.

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5.2 Vocabulary

• Following this section, I will be able to define
• 4. banked curve
• 5. blowout
• 6. friction
• 7. tread

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Footprints

• What are the footprints that are created by your
  tires?
• What is the force that keeps each tire from
  sliding on the road?
• The friction created by the tire on the road is
  called _____________ and makes its possible for
  your vehicle to grip the road so you can change
  speed and direction.

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Tires Tread and Traction

• Tread- the grooved surface of a tire that grips
  the road.
• What is the purpose of tread?
• A worn, bald tire is dangerous. It has very
  little, if any, grip on the road. May easily
  puncture and end in a blowout.

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Inflation and Traction

• See pictures on page 95- What causes each and
  what could the results be?
• Proper inflation-
• Underinflation-
• Overinflation-

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Split Traction

• The amount of available traction is divided
  between stopping or starting and steering.
• An example would be a curve. Some traction would
  be used for turning and some for braking. Slow
  down before the curve, maintain advised speed
  through the curve, accelerate when coming out of
  the curve

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Reduced Traction

• Two things are needed to maintain ideal traction
• 1. Your vehicle must be in good condition.
• 2. The road must be paved, smooth, level, and
  clean.

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Checking Traction

• Three steps that you can follow to check to see
  how much traction you have
• 1. Check you rear zone to make sure no traffic
  is near.
• 2. Brake gently to see how your vehicle
  responds.
• 3. If your vehicle does not slow or if your
  antilock brakes start to work, reduce speed even
  further.

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Curves

• Energy of motion (centrifugal force) and traction
  will work on your vehicle as you drive around a
  curve.
• Your vehicles speed, the sharpness of the curve,
  the bank of the curve, and your vehicles load
  will affect the control you have in a curve.
  (see picture on p. 97)

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Review

• How can traction control your vehicle?
• What are three things that can reduce your
  traction?
• What three steps can you take to check traction
  while driving?
• Name three factors that can affect your vehicle
  in a curve.

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5.3 Stopping Distance

• This section focuses on stopping distance,
  reaction time, reaction distance, and braking
  distance. You will learn how to estimate
  stopping distance at different speeds. Factors
  that affect braking distance are discussed.
• Following this section, I will be able to
• Define total stopping distance.
• Explain how to use the four second rule.
• Name four factors that affect braking distance.

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5.3 Vocabulary

• Following this section, I will be able to define
• 8. Braking distance
• 9. Perception distance
• 10. Perception time
• 11. Reaction distance
• 12. Reaction time
• 13. Total stopping distance

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Stopping Distance

• When you are driving and have to stop, three
  things must happen. You must perceive the hazard
  in your path of travel, react, and brake your car
  to a stop.
• Total stopping distance- The distance your
  vehicle travels while you make a stop.

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Perception Time and Distance

• Perception time- The length of time it takes to
  identify, predict, and decide to slow down for a
  hazard. This will vary.
• Perception distance- The distance your vehicle
  travels during the perception time.

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Reaction Time and Distance

• Reaction time- Once you recognize a hazard, the
  length of time you take to execute your action.
  (Average driver will take ¾ of a second to
  react.)
• Reaction distance- The distance your vehicle
  travels while you react.

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Braking Distance

• Braking distance- The distance your vehicle
  travels from the time you apply the brake until
  you stop.
• If you accelerate from 20 mph to 40 mph, your
  braking distance will be about four times longer.
  (Refer to chart on p. 98.)

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Estimating Stopping Distance

• 1. Pick a fixed checkpoint ahead where you
  think you could stop.
• 2. Count off four seconds.
• 3. Check your vehicles position. If you have
  just reached your fixed checkpoint, you can
  assume the distance you estimated in step 1 was
  the approximate distance it would have taken you
  to stop.
• Note It will take approximately 300 (length of
  football field) to stop at 65 mph. (See chart on
  p. 99)

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Factors That Affect Braking Distance

• Seven factors that can affect your total stopping
  distance
• 1. Speed-
• 2. Vehicle condition-
• 3. Roadway surface-
• 4. Driver ability-
• 5. Antilock Braking System (ABS)-
• 6. Hills-
• 7. Loads-

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Review

• 1. What three parts add up to your total
  stopping distance?
• 2. How can you estimate your stopping distance?
• 3. What factors can affect your braking distance?

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5.4 Controlling Force of Impact

• This section focuses on the force of impact in a
  collision. The benefits of restraint devices are
  discussed.
• Following this this section, I will be able to
• 1. List three factors that will change your
  vehicles force of impact in a collision.
• 2. Explain the correct way to adjust safety
  belts.
• 3. Describe how a driver and passengers should
  position themselves to benefit from air bags.
• 4. Explain how to best position and use child
  safety seats.

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5.4 Vocabulary

• At the conclusion of this section, I will be able
  to define
• 14. active restraint device-
• 15. force of impact-
• 16. passive restraint device-
• 17. restraint device-

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Force of Impact

• Force of impact- The force with which a moving
  object hits another object.
• Three factors determine the force of impact
• 1. Speed-
• 2. Weight-
• 3. Distance between impact and stopping-

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Safety Belts

• Three collisions occur when a vehicle hits a
  solid object
• 1. Vehicle hits object and stops
• 2. Occupant hits inside of vehicle or their
  restraint devices.
• 3. Occupant may suffer internal collisions as
  their organs impact the inside of their bodies.

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Safety Belts

• Passive restraint device- i.e., an air bag that
  works automatically
• Active restraint device- i.e., safety belt that
  must be engaged

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How to Wear Safety Belts

• 1. Adjust your safety belt to a comfortable
  upright position. Make sure your safety belt is
  not twisted.
• 2. Snap safety belt into buckle. Adjust lap
  part of safety belt so that it is low and snug
  across your hips. The bottom edge of the belt
  should touch your thighs. This keeps the belt
  low and any crash forces will be applied to your
  pelvic bones and not your internal organs.
• 3. Adjust shoulder part of safety belt across
  your chest. Shoulder belt should be snug.

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Air Bags

• A balloon-type device that automatically inflates
  at the blink of an eye at speeds of over 200 mph.
• To receive full benefit from an air bag
• 1. It is a supplemental restraint device
  designed to work with safety belts.
• 2. Keep hands at 9 3 oclock or 8 4 oclock
  on the steering wheel.
• 3. 10 between driver steering wheel.
  Passenger should be back as far as possible.
• 4. Steering wheel tilted toward your chest.
• 5. Children up to age of 12 must sit in back
  seat to avoid injury from air bag deployment.

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Air Bag Improvements

• Air bags have proven to be an effective
  life-saving device. Engineers are now working to
  make them even more effective.
• Advanced airbags- deploys in two stages like a
  bag within a bag.
• Air bag switches- operator controlled on/off
  switch

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Other Protection Devices

• 1. Automatic safety belts-
• 2. Front and rear crash areas-
• 3. Energy-absorbing bumpers-
• 4. Side door beams-
• 5. Reinforced windshield-
• 6. Energy-absorbing steering wheel and column-
• 7. Padded dash-
• 8. Child seats- (see picture on p. 103)
• 9. Head restraints-

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Review

• 1. What three factors can affect force of
  impact?
• 2. What three steps should you take when putting
  on safety belts properly?
• 3. What are the two key steps you should take to
  protect yourself as the driver of a car with air
  bags?
• 4. Where should all child seats be secured in a
  car?