Natural Laws and Car Control Chapter 5 Natural Laws and Car Control

5.1 Gravity and Energy of Motion Is a force that pulls all objects toward the center of earth Effects of Gravity When you drive uphill your car can lose speed as it works against the force of gravity. You must increase power (accelerate) to maintain speed The force of gravity also tends to increase the speed of cars going downhill. You need a longer distance in which to stop.

5.1 Gravity and Energy of Motion Center of Gravity The point around which all an object’s weight is evenly balanced Most cars have a low center of gravity so they will handle well in turns A car will handle differently when its center of gravity is raised. It will be less stable in curves and during quick maneuvers

5.1 Gravity and Energy of Motion Energy of Motion (Kinetic Energy) The energy an object has because it is moving The faster a car moves the more energy of motion it will have. The car will be harder to control Mass=Weight A vehicle’s energy of motion doubles when its weight doubles. When the vehicles weight doubles, the vehicle needs about twice the distance to stop Velocity=Speed A vehicle’s energy of motion is proportional to the square of its increase in speed. When the vehicle’s speed doubles, the vehicle needs about four times the distance to stop. When, the vehicle’s speed triples, the vehicle needs nine times the distance to stop. Kinetic Energy Video - http://www.youtube.com/watch?v=vl4g7T5gw1M

5.2 Friction and Traction Friction The gripping action which keeps, each tire from slipping when the tires rest or move on the road Traction Friction or gripping power between a tire and the road. Traction allows a car to grip the road so it can speed up, slow down, and turn http://www.youtube.com/watch?v=06W4qvhZEEc Tread The grooved surface of a tire that grips the roadway. In rain it allows the water to flow through the grooves and away from the tire Bald tires – worn out tread Overinflated – only the center of the tire provides traction Underinflated – only the outside edges of the tire provide traction Two areas of the roadway that freeze first – bridges, shady areas Show Video –Advanced Auto Parts (Tire Safety – 1:21 min) or http://www.youtube.com/watch?v=zA6MUlVNkLM

5.2 Friction and Traction Curves – Factors that affect the control you have over your car in a curve Speed – adjust speed before entering the curve. Follow any posted advisory speed limit signs Sharpness of a Curve – use lower speeds for sharper curves Bank of a Curve – a curve that is higher on the outside than it is on the inside. This tilt improves control by working with the force of gravity Load – a vehicle’s load determines its ability to handle curves http://www.youtube.com/watch?v=1STGU6BeND8

5.3 Stopping Distance Total Stopping Distance The total distance it takes to stop a car Includes: Perception distance + reaction distance +braking distance =total stopping distance http://www.youtube.com/watch?v=mDWCen_09o8

5.3 Stopping Distance Factors that affect braking distance Speed The higher the speed, the longer the braking distance Car Condition Cars with worn tires, bad shock absorbers, old brakes need a longer distance to brake Roadway Surface Rain, snow, ice, gravel, leaves – increases braking distances Driver Reaction Hills Load

5.4 Controlling Force of Impact The force with which one moving object hits another Three factors determine how hard the force of impact will be when a car hits another object Speed Weight Distance between impact and stop

5.4 Controlling force of impact 10 Safety Devices that protect you in an accident Seatbelt Air Bag Front and Rear crush areas Energy Absorbing bumpers Side door beams Reinforced Windshield Energy Absorbing steering wheel and column Padded Dash Head Restraints Child safety seats Drive Right Video Chapter on Natural Laws