Drivers Ed 4: Physics and Natural Laws

Impact Force is Small

A rear-end collision produces a much smaller amount of FOI,

Applying the brakes causes friction.

Friction produces heat . The friction converts the kinetic energy into static (not-in-motion) energy. The more kinetic energy a vehicle has, the more heat is required to do the conversion.

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

Inflate them to the recommended pressure

Kinetic Energy formula:

KE = 1/2M x V

How Fast Am I Going?

Take your Speed, add 1/2 your Speed. The result is your speed in feet per second.

How Long Will it Take to Stop?

Take your speed, multiply it by 1/10 of your speed and divide the result by two. The result is your stopping distance, after the brakes are applied, in feet.

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)

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

Friction is:

-increased by the weight of your vehicle -decreased if your tires are over-inflated or -under-inflated -decreased 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)

To keep your vehicle from rolling away, you should

-leave your vehicle in a low gear or in "Park" if it has an automatic transmission. -You should always engage your parking brake and you may even need to block your wheels by placing an object in front or behind of the tires.

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.

Impact Force is Medium

A "sideswipe" collision reduces the FOI, and is a goal for any driver faced with a "Gonna hit!" situation.

Impact Force is High

A T-Bone, or side-impact, collision is the next deadliest when it comes to FOI.

Impact Force is Highest

A head on collision produces the highest impact force.

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

Decrease the velocity

Centrifugal force:

Doesn't really exist

Do you want a lot of friction while driving?

Yes, skipping will occur if due to the breaks friction being higher, so you want normal road conditions and correct tires

Friction is:

a force caused by the contact of one surface on another.

To lower the friction on these parts, manufacturers use

a lubrication system to provide a thin film of oil or grease between the moving parts. This is the same thing that happens when you squirt oil on a squeaky door hinge.

If you are parking facing downhill, you should:

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

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

gravity inertia momentum kinetic and potential energy friction centrifugal force

Disc brakes

have a good ability to dissipate the heat quickly (the RED areas), so that more heat can be used to bring the car to a complete stop.

Banked roadways

improve your traction in turns. They help in overcoming the centrifugal force that is pulling you away from the direction in which you want to turn.

Kinetic energy:

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

Centrifugal force is:

is the tendency for objects to be pulled outward when rotating around a center

If two vehicles are involved in a collision moving at the same rate of speed, the vehicle that weighs

less will take the greater impact.

How Long Will it REALLY Take?

since it takes about one second to recognize a danger and then react to it, add the distance you travel in one second to the stopping distance to find the total distance, in feet, it will take you to stop. (S + 1/2S) + (S x 1/10 S /2) = Total Stopping Distance (feet)

Any increase in the velocity (speed) of the vehicle will increase

the KE by the square of the change in speed. Doubling the velocity will quadruple the KE.

Potential energy is

the energy that an object possesses because of its position or form.

Traction is:

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.

f 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.

Inertia causes

your body and loose objects in your car to keep moving forward when your vehicle stops suddenly.

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.

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.

The friction on your brakes and clutch results in brake and clutch wear. If used improperly, 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)