lesson 4

The Law of Inertia

(an object in motion, remains in motion, in a straight line, at a constant speed, until acted upon by an unbalanced force), is what keeps a car going straight down the highway, with minimal steering effort.

kinetic energy

(motion) the energy a body possesses because it is in motion.

The Law of Gravitation

(one object attracts another, via a straight line, drawn between the objects' center. The larger the mass the stronger the attraction) is why cars slow down on a hill (moving away from the center of the earth) and why roads are "banked" in curves, to keep the car on the roadway

Sir Isaac Newton (1643 - 1727) was an English scientist. His discoveries and theories in "nature's laws" lead to Newtonian Physics, and his famous laws, including

-The Law of Inertia -The Universal Law of Gravitation -The Law of Motion and Acceleration -The Law of Reciprocal Action

You can reduce the forces on you and your car during an unavoidable crash if you are able to redirect your path toward objects that will cause your car to stop over a greater distance, such as:

-bushes rather than trees -snow -soft dirt -sand barrels placed in front of freeway abutments

In order to keep a vehicle in a turn without allowing centrifugal force to pull the car out, you should:

-decelerate before the curve -brake gently and gradually while turning -downshift (manual transmission)

excessive wear to the brake pads and clutch can occur. To avoid this:

-do not ride your brakes -do not drive with your clutch partially engaged (depressed) -use your lower gears to slow the vehicle on downhill grades (downshift)

Gravity decreases your kinetic energy when you are driving uphill and increases it when you are driving downhill. Therefore, the force of gravity will make it:

-easier to stop your car if you are going uphill -more difficult to stop your car if you are going downhill

The kinetic energy of your moving vehicle determines your ability to stop the car. In addition to the distance traveled due to your reaction time, your stopping distance will be:

-four times further if you increase your speed from 10 MPH to 20 MPH -25 times further if you increase your speed from 10 MPH to 50 MPH.

When you make a controlled stop, the momentum of your vehicle must be overcome by the:

-friction force of your brakes -friction force between your tires and the road -compression force of your engine

There are many natural forces acting on your vehicle, such as:

-gravity -inertia -momentum -kinetic and potential energy -friction -centrifugal force

Friction can be altered by changes in the road surface, where your tires make contact. Road surfaces change due to:

-ice -rain -snow -oil and diesel fuel buildup -sand or dirt will reduce the traction of your tires

The kinetic energy of your body while it is in motion, of loose objects in the car, and of the car itself, all increase with weight (mass) and the square of your speed so that:

-if you increase your speed from 10 MPH to 20 MPH, you are dealing with four times the amount of kinetic energy -if you increase you speed from 10 MPH to 50 MPH you have to deal with 25 times the amount of kinetic energy

Friction is:

-increased by the weight of your vehicle -decreased if your tires are over-inflated or under-inflated -increased if the tires are worn smooth -affected by the material used to construct the road -affected by the condition of the surface of the road (including factors due to weather)

In a crash

-the kinetic energy of your vehicle and body must be dissipated -the forces needed to dissipate this energy are lower if the time period over which your vehicle moves during the crash is longer -if the car suddenly stops, the forces will be very high.

KE =

1/2 MVKinetic Energy = one-half the Mass times Speed squared

According to the formula for stopping distance, how many feet will it take you to stop, from 60 mph

180

The primary factor in decreasing the Kinetic Energy of an object is to:

Decrease the velocity

The best way to maximize the traction of your tires is to:

Inflate them to the recommended pressure

Maxium Tread Contact =

Maximum Friction

Because friction is increased by the weight of your vehicle

a fully-loaded truck has more stopping power than does an empty one because it is heavier. The weight aides in stopping the vehicle by producing more friction between the tires and the road surface.

As you increase your driving speed, both your body and your vehicle acquire kinetic energy which eventually must be

absorbed by your brakes, engine compression forces, or other friction in a controlled stop absorbed by your body, your vehicle's body, and the objects you hit if you are involved in a crash.

Air bags treat your head as a water balloon, and, by slowly deflating, they "catch" your head

allowing it to move forward with slower speeds, and preventing impact with the steering wheel

Potential energy

is the energy that an object possesses because of its position or form. For example, a book on a table has the "potential" energy to fall to the floor, whereas a book that is already on the floor has the potential energy to "fall" towards the center of the earth.

The force of a moving object is called

momentum.

All drivers are subject to the

natural laws and laws of physics that affect any moving, or stationary, object.

Gravity

the force that pulls all objects towards the center of the earth. Gravity also affects your speed of travel when going uphill and downhill because of the change in gravitational pull as you move towards, or away from, the center of the earth.

Traction

the result of friction between the road and your tires caused by the weight (gravity effect) of the car pushing the tires to the road due to gravity. Traction is necessary for you to steer your car.

Centrifugal force

the tendency for objects to be pulled outward when rotating around a center. Physics teachers will often say that centrifugal force isn't actually a force at all,It is actually the inertia of an object, tending to go in a straight line

When you drive downhill, the reverse is true. Gravity will cause you

to go faster and increase your stopping distance

When you are driving uphill, the force of gravity is

working against you to slow you down and you may need to accelerate or change to a lower gear to maintain your speed.

If you are parking facing downhill

you should always turn your front wheels towards the curb or side of the road.

If you are parking facing uphill and there is a curb

you should turn your front wheels towards the middle of the road and allow the vehicle to roll back against the curb.

If you are parking facing uphill and this is not a curb

you should turn your wheels toward the side of the road.