Transcript Natural Laws - Washington County School District

Natural Laws
6 THAT EFFECT DRIVING
•UNDERSTANDING THE NATURAL FORCES THAT AFFECT YOUR DRIVING
•TAKE INTO ACCOUNT THE EFFECT OF NATURAL FORCES AS YOU DRIVE
•RECOGNIZE FACTORS INFLUENCING TRACTION, DIRECTIONAL CONTROL AND CORNING.
WHEN DRIVING
• YOU SHOULD BE AWARE OF THESE FORCES.
• THEY ARE IMPORTANT IN CONTROLLING THE MOVEMENT OF
YOUR CAR ON THE ROAD
1. ENERGY OF MOTION
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KNOWN AS KINETIC ENERGY
THE ENERGY OF MOTION
SOMETIMES CALLED MOMENTUM
KINETIC ENERGY OF A MOVING CAR OR OTHER VEHICLE
INCREASES WITH MASS (WEIGHT) AND VELOCITY (SPEED)
THE FORMULA IS KE=1/2MV2
SO BY DOUBLING THE WEIGHT OF A VEHICLE IT DOUBLES THE
ENERGY OF MOTION AND AN INCREASE SPEED HAS AN EVEN
GREATER EFFECT ON THE ENERGY OF MOTION.
2. GRAVITY
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GRAVITY ALSO HAS AN EFFECT ON THE SPEED OF THE CAR.
GOING DOWNHILL, THE FORCE OF GRAVITY WILL CAUSE IT TO
INCREASE SPEED.
BY USING THE BRAKES YOU CAN KEEP THE CAR FROM
INCREASING SPEED TOO MUCH
YOU CAN ALSO USE ENGINE BRAKING (RELEASING THE AMOUNT
OF PRESSURE PLACED ON THE ACCELERATOR)
GRAVITY CAN ALSO HAVE AN EFFECT ON THE AMOUNT OF TIME
AND SPACE NEEDED TO STOP A CAR GOING DOWNHILL. IT WILL
TAKE LONGER TO STOP IF YOU ARE MOVING DOWNHILL.
3. FRICTION
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FRICTION IS A FORCE WHICH ALWAYS ACTS IN THE OPPOSITE
DIRECTION OF THE MOTION OR FORCE APPLIED.
FRICTION IS THE RESISTANCE BETWEEN THE MOVING TIRES AND
THE PAVEMENT.
FRICTION BETWEEN THE TIRES AND ROAD SURFACE IS CALLED
TRACTION.
WITHOUT TRACTION WE WOULD NOT BE ABLE TO STOP, TURN, OR
EVEN KEEP THE CAR MOVING.
FACTORS AFFECTING
TRACTION
• TIRES – ARE DESIGNED WITH GROOVED SURFACES THAT
TOUCH THE ROAD.
• THESE ARE REFERRED TO AS THE TREADS.
• CONDITIONS OF THE TIRES AFFECTS THE AMOUNT OF
TRACTION THEY WILL HAVE “BALD TIRES” PROVIDE VERY
LITTLE OR NO TRACTION ON WET, ICY, OR SNOW-COVERED
ROADS.
4. INERTIA
• SIR ISAAC NEWTON WAS A BRITISH SCIENTIST WHO
FOUNDED THE SCIENCE OF MECHANICS.
• MECHANICS IS THE STUDY OF MOTION AND THE CAUSES OF
CHANGES IN MOTION.
• THE FIRST LAW OF MOTION IS CALLED THE LAW OF INERTIA.
• IT STATES THAT AN OBJECT IN MOTION WILL CONTINUE TO
MOVE IN A STRAIGHT LINE UNLESS SOME FORCE ACTS
AGAINST IT.
• AN OBJECT AT REST WILL REMAIN AT REST UNLESS SOME
FORCE ACTS ON IT.
5. CENTRIFUGAL FORCE
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IS THE TERM USED TO DESCRIBE THE FOCE THAT TENDS
TO PUSH A MOVING OBJECT OUT OF A CURVE OR TURN
INTO A STRAIGHT PATH.
ACTUALLY THIS TENDENCY CALLED CENTRIFUGAL FORCE
IS REALLY CAUSED BY INERTIA.
THREE FACTORS DETERMINE THE AMOUNT OF
CENTRIFUGAL FORCE.
THE SHARPNESS OF THE TURN.
THE SPEED OF THE VEHICLE
THE SIZE OF THE VEHICLE.
6. FORCE OF IMPACT
• THE FORCE WITH WHICH ONE OBJECT COLLIDES WITH
ANOTHER.
• IN A COLLISION THE FASTER AND HEAVIER A VEHICLE, AND
THE MORE SOLID THE OBJECT IT IS COLLIDING WITH, THE
MORE DAMAGE IS DONE.
SEAT BELTS
• According to a recent research report from the
National Highway Traffic and Safety Administration,
seatbelts save 13,000 lives in the United States each
year. Meanwhile, the NHTSA estimates that 7,000
U.S. car accident fatalities would have been avoided
if the victims had been wearing belts. While seatbelts
do occasionally contribute to serious injury or death,
nearly all safety experts agree that buckling up
dramatically increases your chances of surviving an
accident. According to the NHTSA, seatbelts reduce
the risk of death for a front seat car occupant by
about 50 percent.
HOW DO THEY WORK
• A typical seatbelt consists of a lap belt, which rests over your pelvis,
and a shoulder belt, which extends across your chest. The two belt
sections are tightly secured to the frame of the car in order to hold
passengers in their seats.
A spiraled spring
rotates the spool to
keep the seatbelt
webbing taut.
SEATBELTS
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The retractor has a locking mechanism
that stops the spool from rotating when the
car is involved in a collision. There are two
sorts of locking systems in common use
today:
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systems triggered by the car's movement
systems triggered by the belt's movement