Chapter 11: MotionSection 3

Standards

Standard 3 MotionInvestigate the relationships among

speed, position, time, velocity, and acceleration

Objectives List the four fundamental forces of nature

Explain the term net force

Contrast balance and unbalanced forces

Describe the two different types of friction

Explain the differences between wanted and unwanted friction

There are FOUR fundamental forces which are they?

GravityFrictionWind/WaterElectromagneticSlidingAttractionWeak Nuclear

SolarStaticTorsionStrong nuclearField Contact

Objective 1: List the four fundamental forces of natureAnd the FANTASTIC FOUR are…

The IMPRESSIVE Twosome

Gravity Acts over large

distances Experienced every day

Electromagnetic Acts over large

distances Deals with electricity

and magnets

The TROUBLESOME Two

Strong Nuclear Acts over short distances Strongest force Holds together the

atomic nucleus Weak Nuclear

Acts over short distances Responsible for

radioactive decay

TUG O WAR!!

Explain what happens! Net force

Sum of all forces acting on an objectWhen net force acts on an object…

The object will accelerate in the direction of the force

Example: when playing tug of war the side that is pulling with the most force accelerates in the direction of the other side

Objective 2: Explain the term net force

The Balancing Act

Balanced Forces Net force is equal to

zero!! Do NOT cause an object

To accelerate To change motion

Examples: Book sitting on a desk You sitting in your

chair Moving at a constant

speed in one direction

Unbalanced Forces Net force is NOT equal

to zero Cause an object

To accelerate To change motion

Examples Speeding up or

slowing down in car Winning tug of war Circular motion!

Objective 3: Contrast balance and unbalanced forces

Video!!

What Caused That?!?

FRICTION!!!!!!!!!! Force that ALWAYS OPPOSES motion

Two types of friction Static friction

Friction between surfaces that are stationary

Kinetic friction Friction between surfaces that are moving

Two types Sliding – when two objects slide against one another

Rolling – when a rounded object rolls over a flat surface

Is usually less than sliding friction

Static friction is always greater than kinetic friction!!!

Objective 4: Describe the two different types of friction

Objective 5: Explain the difference between wanted and unwanted friction

The Love/Hate of Friction! Without Friction…

There would be NO movement!!

What are some ways that friction is helpful?

Walking, sitting in a desk, even writing with a pencil!

What are some ways that we can increase friction?

Making surfaces more rough

Putting sand on the roads or baseball players wearing gloves

What are some ways that friction can frustrate you?

In an engine-friction will rob horsepower or even burn up an engine!

Hinges in doors! The CREAKY door syndrome!

What are some ways to lower friction

The use of lubricants, such as grease or WD-40

Using cooking oil on a pan while cooking