Basic Vehicle Dynamics

Newton’s 3rd Law of Motion

Remember from high school “for every action there is an opposite and equal reaction”. If there is a force pushing on the Center of Gravity (CG) of the vehicle, there has to be an equal and opposite force pushing back – that force pushing back is created by the friction the tires make with the road. When the driver turns the steering wheel to maneuver around a corner or an emergency scenario, there is energy pushing on the CG of the vehicle. The amount of energy is determined by how much the student moves the steering wheel and how fast they are traveling. The more speed and the more steering, the more energy pushing on the vehicle, if they apply too much speed or too much steering the result is under or over steer

The 3rd Law and the Comfort Zone/Red Zone
As drivers we all have a combination of speed and steering that we are comfortable with, and that combination can be called the drivers comfort zone. But in an emergency, the driver will be required to go past their Comfort Zone, way past it into the Red Zone. While approaching the Red Zone, the driver will notice a big difference in how the car reacts to their inputs. The steering wheel and gas pedal become hypersensitive, small changes in steering or speed create big changes in the way the vehicle responds.

All data indicates that going from the Comfort Zone to the Red Zone is measured in tenths of a second, tenths of inches on the steering wheel, and/or 2 MPH. As a trainer you cannot determine this change in speed, timing, or steering by looking at the vehicle or by sitting in the passenger seat looking at the speedometer. The end result is that student performance should  be monitored at all times, and instructor feedback made on objective data. There is nothing the driver does with the vehicle that cannot be measured by a computer or by taking empirical data. This will be the subject of a future post.

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