Seung-Jae You
Sunghun Jun
Which parts of the car
protects the driver from
1. Tires ( Automobiles Tires and Friction)
2. Seatbelt ( Seatbelt and Inertia)
3. Airbag ( Airbag and Momentum & Impulse)
4. Crumple Zone (Crumple zone and Newton’s
Automobiles Tires &
 The friction between the tires of an
automobile and the road determine the
maximum acceleration.
 However, more importantly, it determines
the minimum stopping distance
 The nature of the friction could actually be a
matter of life and death.
 As a result, more friction, more safe
Automobiles Tires &
 How can we increase the friction?
- Increase the coefficient of friction
- If the surface of tire is rougher, then the friction
force is larger
- When a tire contacts dry asphalt ground, the
coefficient of friction increases.
- On the other hand, if the roads are wet, a tire
contacts with water, the coefficient of friction
- ex) hydroplaning
Automobiles Tires &
 Various types of tires
This is an all-season tire. The grooves provide a way for water
to escape, increasing the coefficient of friction. The grooves
are small enough to prevent the bumpy ride of the next tire
The wide deep grooves here allow snow and mud to
penetrate. But they give a noisy bumpy ride on pavement ...
and if the treads get clogged with mud, the treaded tire
essentially becomes a mud-covered 'slick' with a low
coefficient of friction
In extreme mud, these tractor or bush tires can transfer more
force, but the mud doesn't get caught in tiny grooves, so they
retain their traction
Automobiles Tires &
Seatbelt and Inertia
 Newton’s 1st law: an object will move with
constant speed in a straight line except when
acted upon by a net force
 when a driver stops the car suddenly, the
driver fall forwards, because the driver’s body
try to maintain its speed.
 Consequently, a seatbelt holds the driver and
prevents the driver from falling forwards
when the car stops
 Seatbelt increases the time of impact
(impulse and momentum) so that it results
lesser impact
Airbag and Momentum &
Every object has momentum.
Momentum consists of a driver’s mass and velocity
- Momentum (p) and Impulse (FDt)
- p = mv, FΔt = mΔv
 There has to be a force in order to stop the driver’s
 The driver may hits the dashboard or windshield w
hich also acts as a force stopping the driver but it i
njures them at the same time
 By the way. Airbag gives a force over time (Impulse
). The more the the force acts on the driver to slow
him down, the less damage caused to the driver
Crumple Zone
 It is also known as crash
 It absorbs energy from a
collision and reduce the
force of a collision.
 Bending during a car crash
increases time to halt the
 Newton’s first and second
laws are applied to
crumple zone.
Newton’s First Law
 Newton’s First Law (The law of inertia.)
 Many people are injured because of the law
of inertia.
 Although the car stops, the person inside
does not stop.
 An unbalance force, crumple zone, lowers the
tendency of people to move forward in car
Crumple Zone
 Newton’s Second Law
 The second law is expressed in equation form
as F=MA. (F= force, M= mass, A=acceleration)
 A=V/T (V= velocity, T= time)
 More time means less acceleration.
 Less acceleration by increased time reduces
force that applies to people inside of the car.
What new insight does this
topic provide to you
 Many people think tire’s surface guarantee
your safety 100%, but tire’s surface just
makes you safe on the snow, water, or any
other ground.
 Since car body seems easily bend, Some
people think that crumple zone makes the car
less protected.
 However, It is just misconception. In fact,
crumple zone makes car more safe.
What new insight does this
topic provide to you
 A misconception of AWD and 4WD is that
they are safer.
 In fact, they help little bit in cornering and
driving on snow.
 However, it has nothing to do with braking
 AWD and 4WD do not provide additional
ability for steering
 AWD and 4WD do not provide additional
ability for braking.
What new insight does this
topic provide to you
 Even if the car’s safety improve, this is what
happen if you drive too fast
references and bibliography

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