Transcript Cree Enna Christina Dickens Kristin Forrest Louise Jones

Cree Enna
Christina Dickens
Kristin Forrest
Louise Jones
INTRODUCTION
 The
speed limits on city streets should differ
depending on the weather because when it is
raining the tires of a car are more likely to
slide because there is less friction, possibly
causing accidents if the driver does not slow
down.
 One should drive safer on wet surfaces
because the tires of a car are more likely to
slide on wet surfaces than on dry surfaces,
therefore making the force of kinetic friction
lower.
PURPOSE
 People
that drive in the rain are sometimes
not aware of the possible outcomes.
 Although
the speed limit sign does not
change with the weather, one should be
aware that their speed should change.
 To
make people aware of hydroplaning.
COMMON DANGERHYDROPLANING
 Hydroplaning-
is when the driver losses
control due to not slowing down on wet
surfaces.
 Makes the tires lose contact with the road.
 Causes
a loss of friction, making the driver
not able to break or steer at all.
RESULTS OF HYDROPLANING FROM A
PUDDLE OF WATER.
HYDROPLANING CONT’D

“Hydroplaning occurs
when water on the
roadway accumulates
in front of your
vehicle’s tires faster
than the weight of
your vehicle can push
it out of the way.”


(http://www.engr.pitt.edu/s
sc/hydroplaning.html)
Fs= msmg
HYPOTHESIS
 If
we test a rubber-wheeled car with a
constant velocity on wet concrete, dry
concrete, wet asphalt, and dry asphalt, then
the rubber on wet asphalt will have a lower
force of kinetic friction because the wetness
of the surface makes the tires more slick,
and the surface is smoother.
 Basically,
it is easier for a car with locked
tires to be pushed on wet surfaces.
MATERIALS
Calculators for each group member
 1 rubber wheeled toy car
 A level asphalt surface
 A level concrete surface
 Stop watch
 Tape measure or yard stick
 Chalk
 2 Liters of water to wet the surfaces

PROCEDURES




Gather materials.
Make a chart or table on paper to keep track of
the data. The chart or table should include the
surface tested, distance of each trial (2 meters),
the time it took for each trial on each surface,
and the mass of the car. Also an empty column
should be on the side to calculate the frictions.
Pick your first surface.
Measure 2 meters on the surface, and mark the
starting line with Point A, and finishing line
with Point B with the writing utensil.
PROCEDURES
The person doing the timing should be prepared
to start the timer as soon as the front tire passes
Point A.
 Pull the switch on the side of the car back to start
the car to moving at a constant velocity. To stop
the car, push the switch to the front.
 Hold the car so it will not roll, and put it 4 inches
behind the line, to give the time keeper enough
time to prepare.
 Soon as the back wheels pass Point A, the time
keeper must start the stop watch.

PROCEDURES CONT’D
 Observe
the behavior of the toy cars speed
and then record the test results on the data
or chart.
 After the car has passed point B, the time
keeper must stop the timer, and the recorder
must record the time.
 Repeat steps 4-9 for all the surfaces 3 times.
 Gather supplies, and go to a cool place, so the
team members can start to calculate/figure
out the results.
Dry Asphalt
Wet Asphalt
Dry Concrete
Wet Concrete
Trial 1
2.88m/s
2.63m/s
2.78m/s
2.77m/s
Trial 2
2.59m/s
2.60m/s
2.59m/s
2.80m/s
Trial 3
2.71m/s
2.75m/s
2.60m/s
2.68m/s
Average
2.73m/s
2.65m/s
2.66m/s
2.75m/s
The weight of the car is 357.9g = .3579 kg.
Dry Asphalt
Coefficient of
.67
Kinetic Friction
Wet Asphalt
Dry Concrete
Wet Concrete
.53
.68
.58
RESULTS CONT’D
 Fk=
mkmg
Force of
Kinetic
Friction
(Newtons)
Dry
Asphalt
Wet
Asphalt
Dry
Concrete
Wet
Concrete
2.35 N
1.86 N
2.39 N
2.03 N

In conclusion, the rubber on wet asphalt had a
higher force of kinetic friction than the other
surfaces. The hypothesis was accurate and we
were able to warrant our thesis. Though it was
possible for there to not be much of a difference
between the four surfaces, the results showed a
change in the force.
POSSIBLE ERRORS
 The
car could have gotten off course
by the distance between two points.
 The wind was a factor as
contributing to the speed of the car.

Different wind speeds depending on
location of the trials.
FURTHER
EXPERIMENTS
 Experiments





could be tested with…
different car
different surfaces
an obstacle course
weights on the car
weather variants
WORKS CITED
Hyper Physics
http://hyperphysics.phyastr.gsu.edu/hbase/frict2.
html
 Kinetic Friction
http://www.ap.stmarys.ca/demos/content/mechani
cs/kinetic_friction/kinetic_friction.html
 Safety and Security Committee (SSC)
http://www.engr.pitt.edu/ssc/hydroplaning.html
 Speed & Velocity
The Physics Hypertextbook™ © 1998-2008 by
Glenn Elert
http://hypertextbook.com/physics/mechanics/veloc
ity/

SPECIAL THANKS
Mrs. Morgan for supplies
Mrs. Scott for assistance
Mr. Cicenas for physics assistance
Ms. Daphne for Writing tips
Mr. Smith for Writing instructions
Mrs. Vardy for research time
QUESTIONS
THANKS FOR LISTENING!!!!