EVD Physical Forces

EVD2 EVD Physical Forces  Directly Influence Control  Offer Boundaries If Maintained – safe operation If Exceeded – loss of control Ref. Unit IV LP 1 (Lesson 8)

EVD3 EVD Physical Forces  Forces Acting on an Emergency Vehicle Velocity Friction Inertia Momentum Reaction Centrifugal Force Centripetal Force Ref. Unit IV LP 1 (Lesson 8)

EVD4 EVD Physical Forces  Inclement Weather  Excessive Acceleration  Inappropriate Braking  Sudden Direction change Ref. Unit IV LP 1 (Lesson 8)

EVD5 EVD Physical Forces  Velocity (Speed) “Rate of change of position in relationship to time V = 35 feet every second (35 ft/sec) V = 55 miles every hour (55 MPH) Ref. Unit IV LP 1 (Lesson 8)

EVD6 EVD Physical Forces  Velocity Control Acceleration  + Acceleration Deceleration  - Acceleration  (Coasting) Braking  Deceleration using Friction Ref. Unit IV LP 1 (Lesson 8)

EVD7 EVD Physical Forces  Friction “Resistance to motion between to moving objects that are in contact with each other.”  Generates HEAT  Steering Friction  Tire/Road Friction  Brake Friction Ref. Unit IV LP 1 (Lesson 8)

EVD8 EVD Physical Forces  Friction Tire/Road  Greatest – Stationary  Ok – Motion on Dry, Smooth Road  Least – Locked/Spinning Locked – Wheel NOT turning Spinning – Wheel FREE turning Ref. Unit IV LP 1 (Lesson 8)

EVD9 EVD Physical Forces  Friction Brakes  Brakes on Drums / Pads on Discs  Friction Generates Heat Heat Causes Brake Fade Will Break-down Bonding Material Heat/Expand Brake Fluid Ref. Unit IV LP 1 (Lesson 8)

EVD10 EVD Physical Forces  Brakes Shoes / Drums  90%-10% / Contact-Cooling  Excessive Heat = Less Contact Pad / Disc  85%-15% / Cooling-Contact  Excessive Heat = More Contact Ref. Unit IV LP 1 (Lesson 8)

EVD11 EVD Physical Forces  Brakes Locking Wheels Threshold Braking Ref. Unit IV LP 1 (Lesson 8)

EVD12 EVD Physical Forces  Inertia “The force it takes a moving object to stay in motion in the same direction.” Ref. Unit IV LP 1 (Lesson 8)

EVD13 EVD Physical Forces  Newton’s First Law: The Law of Inertia Ref. Unit IV LP 1 (Lesson 8) “An object continues in its state of rest, or uniform motion in a straight line, unless it is acted upon by a net external force.”

EVD14 EVD Physical Forces  Newton’s First Law: The Law of Inertia Ref. Unit IV LP 1 (Lesson 8) Objects resist change More Mass = More Inertia

EVD15 EVD Physical Forces  Momentum Mass x Velocity Ref. Unit IV LP 1 (Lesson 8)

EVD16 EVD Physical Forces  Newton’s Second Law: The Law of Momentum Ref. Unit IV LP 1 (Lesson 8) “When an unbalanced force acts on an object, the object will be accelerated. The acceleration will vary directly with the applied force and will be in the same direction as the applied force. It will vary inversely with the mass of the object.”

EVD17 EVD Physical Forces  Newton’s Second Law: The Law of Momentum Ref. Unit IV LP 1 (Lesson 8) More momentum = more energy to change 1 1 ft/sec = 1 unit of momentum Momentum & Intertia: WORK AGAINST THE DRIVER

EVD18 EVD Physical Forces The Law of Conservation of Momentum Ref. Unit IV LP 1 (Lesson 8) “For a collision occurring between two objects, the total momentum before the collision is equal to the total momentum after the collision.” “When two objects interact, exactly equal and opposite forces result; positive and negative forces balance out.”

EVD19 EVD Physical Forces The Law of Conservation of Momentum Ref. Unit IV LP 1 (Lesson 8)

EVD20 EVD Physical Forces  Reaction “For every action there is an equal and opposite ‘reaction.’” Ref. Unit IV LP 1 (Lesson 8)

EVD21 EVD Physical Forces  Newton’s Third Law: The Law of Reaction Ref. Unit IV LP 1 (Lesson 8) “For every action there is an equal and opposite reaction.”

EVD22 EVD Physical Forces  Newton’s Third Law: The Law of Reaction Ref. Unit IV LP 1 (Lesson 8) Tires push “backward” on the road Road pushes “forward” on vehicle

EVD23 EVD Physical Forces  Centrifugal Force An inertial force which moves a body away from the center of rotation. Ref. Unit IV LP 1 (Lesson 8)

EVD24 EVD Physical Forces  Centripetal Force Forces directing the body towards the center of rotation.  Gravity  Friction Ref. Unit IV LP 1 (Lesson 8)

EVD25 EVD Physical Forces  Centripetal Force vs. Centrifugal Force Forces acting in direct contrast to Centrifugal force. Ref. Unit IV LP 1 (Lesson 8)

EVD26 EVD Physical Forces  Directional Control Steering Turning “Tracking” curves Ref. Unit IV LP 1 (Lesson 8)

EVD27 EVD Physical Forces  Potential Energy Capability – i.e. Coiled Spring Relative to position “Stored” energy Ref. Unit IV LP 1 (Lesson 8)

EVD28 EVD Physical Forces  Kinetic Energy Relative to motion = ½mv 2  m = mass  v = velocity Ref. Unit IV LP 1 (Lesson 8)

EVD29 EVD Physical Forces  Control ONLY  VELOCITY  & DIRECTION Ref. Unit IV LP 1 (Lesson 8)

EVD30 EVD Physical Forces  Control Velocity  Acceleration Change in Velocity + Acceleration = increase - Acceleration = decrease  (Deceleration)  Double Mass = Double Acceleration  Generally thought of in the + Ref. Unit IV LP 1 (Lesson 8)

EVD Vehicle Characteristics

EVD32 EVD Vehicle Characteristics  Weight GAWR Gross Axle Weight Rating GVWR Gross Vehicle Weight Rating Ref. Unit IV LP 2 (Lesson 9)

EVD33 EVD Vehicle Characteristics  Weight GVW Distribution Ref. Unit IV LP 2 (Lesson 9) +/- 7% 2/3 1/3

EVD34 EVD Vehicle Characteristics  Weight Center of Gravity Ref. Unit IV LP 2 (Lesson 9)

EVD35 EVD Vehicle Characteristics  Suspension Axles Rated to carry GVW Springs Rated to carry GVW Wheels Load rated hub Tires Rated to carry GVW Ref. Unit IV LP 2 (Lesson 9)

EVD36 EVD Vehicle Characteristics  Suspension Tires  40 sq. in. Road Contact  4/32 Min. Tread Ref. Unit IV LP 2 (Lesson 9)

EVD37 EVD Vehicle Characteristics  Brakes ABS  Wet/icy roads  Works with disc and drum Auxiliary  NFPA 1901 – 36,000 lbs.  Engine (“Jake”) > 20 mph  Automatic Transmission Retarders  Driveline Retarders Ref. Unit IV LP 2 (Lesson 9)

EVD38 EVD Vehicle Characteristics  Water/Liquid Surge NFPA 1901 NFPA 1902 Baffling Ref. Unit IV LP 2 (Lesson 9)