FRICTION
What is it, & what
does it do?!
11/24 (p. 62)
Friction Notes
• IQ: Graph the following motion on a
speed/time graph:
• A bowling ball goes at a const. speed
(O-A), then goes uphill for some time
(A-B), and then rolls back down (B-C).
• Think about what will happen to the
speed during the various parts of
the movement.
Possible answer
s
t
•
•
Friction is the force that 2 surfaces
in contact exert on each other. It
opposes motion.
A force is a push or a pull on an
object.
Friction always occurs in the
direction parallel and opposite to the
direction of motion.
Does NOT depend upon the
surface area in contact!
Results of friction:
• Friction opposes motion, produces
heat, and causes wear and tear of
surfaces. Ex. machinery, car
tires, shoe soles.
• Friction helps us:
Hold on to things, Clean/scrub, Walk
and drive (both need us to grip the
surface to be able to move), come to
a stop.
Types of Friction
1. Static Friction: The friction that
acts on objects when a force is
applied and they do not move.
For example: static friction can
prevent an object from sliding
down a sloped surface.
2. Sliding Friction: The force that
occurs when 2 solid surfaces slide
over each other, less than static
friction. Ex. sledding, writing with
pencil, scrubbing a dirty surface.
3. Rolling Friction: is the frictional
force of an object rolling across a
surface, less than static and sliding.
One of the most common examples of
rolling friction is the movement of
car tires on a roadway, a ball rolling.
4. Fluid Friction: frictional forces
between a solid and fluid (gas or liquid)
Ex: a hot air balloon flying through the
air, airplane (air resistance), submarine,
a meteor.
Skydiving
• Mythbusters phone book challenge (2
min)
Friction
Reducing Friction
A. Lubricants (Oil, Wax, and Grease)
B. Friction can be reduced by switching
from sliding to rolling friction (adding
wheels or ball bearings)
C. Make surfaces smoother (Sandpaper and
Wood)
Which type of friction? (left
hand side page)
• Snowboarding
• Resting on the side of a hill on your
snowboard.
• Water skiing
• Opening a jar of mayonnaise (between
your hand and the lid)
• Sliding on marbles
• Bungee jumping
Spaceship Columbia Explosion due to heat caused by air
resistance:
• Columbia was destroyed during re-entry on the return from the 113th
shuttle mission on Feb. 1, 2003. All seven astronauts onboard lost their
lives. Columbia was returning from a 16 day mission to conduct
experiments in low Earth orbit.
• The thermal protection system of the space shuttle is designed to
protect the orbiter from the fiery heat of re-entering the atmosphere.
This heat is caused by friction generated by the orbiter traveling at
17,000 mph. About 27,000 thermal tiles are bonded to the orbiter to
protect the bottom and sides from temperatures of over 2000 degrees
F. This area of the orbiter can heat up to 3000 degrees during re-entry.
• The disaster was caused by damage to the orbiter's thermal protection
system that occurred during the launch on Jan. 16, 2003. A small piece
of foam from the external tank broke off and slammed into the leading
edge of the left wing 82 seconds after take-off. It punched a hole
approximately 6-10 inches wide in RCC panel #8. This hole allowed
superheated gasses to enter the wing during the fiery re-entry and led
to the destruction of Columbia only 16 minutes before the planned
landing.
• Friction Video (3 min.)
OQ: If possible, would you like to live in a
friction free world where everything is
frictionless? Support your answer.
• Friction is the __________ that 2
__________ in __________ exert
on each other. It _____________
motion.
• A force is a push or a pull on an
object.
Friction always occurs in the direction
_________ and __________ to the direction
of motion.
Strength of friction depends on:
a. How hard the 2 surfaces are
________
on each other.
B. type of surfaces in contact- how
________ or )__________.
Does ________ depend upon the
______________in contact!
Results of friction:
• Friction _____________ motion,
produces__________, and causes
________ and _______ of surfaces.
Ex. machinery, car tires, ______
soles.
• Friction helps us:
_________ on to things, _______/scrub,
_________and drive (both need us to
__________the surface to be able to
move), come to a __________.
Types of Friction
1. Static Friction: The friction that
acts on objects when a ________
is applied and they do _____
________.
For example: static friction can
_______ an object from
_______ down a sloped surface.
2. Sliding Friction: The force that
occurs when 2 solid surfaces ______
over each other, _______ ______
static friction. Ex. __________,
writing with pencil, __________ a
dirty surface.
3. Rolling Friction: is the frictional
force of an object rolling across a
surface, less than _________ and
____________. Why it’s faster to
skate vs. slide.
One of the most common examples of
rolling friction is the movement of
car ________on a roadway, a ball
rolling.
4. Fluid Friction: frictional forces
between a solid and fluid (_________
or _________)
Ex: a hot air balloon flying through
the air, _____________ (air
resistance), __________, a meteor.
Reducing Friction
A. Lubricants (________, Wax, and Grease)
B. Friction can be reduced by ________ from
sliding to ____________ friction. (Adding
wheels or ball bearings).
C. Make surfaces _____________.
(Sandpaper and Wood)