What is it, & what does it do?! 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 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 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)