NSTA Web Seminar:

Force and Motion: Stop Faking It!

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Thursday, December 11, 2008

Force and MotionForce and MotionSpeed and velocity

Inertia and acceleration

Newton’s second law

Mass and weight

Speed and velocity

Inertia and acceleration

Newton’s second law

Mass and weight

Speed and velocity

Which animal had the greatest average speed for the entire race?

Tortoise Hare

Which animal had the greatest instantaneous speed during the race?

Tortoise Hare

Definitions

Average

Instantaneous speed = speed calculated over an infinitesimally

small time period

Which of the following is true?

All the balls moved exactly alike.

All the balls moved with the same speed.

All the balls were the same color.

They weren’t really balls, it’s a computer simulation.

Let’s Pause for Two Questions from the

Audience

Inertia and Acceleration

Inertia = the tendency of an object to keep on doing whatever it is doing, whether in motion at a

constant speed or at rest

Acceleration = any change in speed and/or direction

Let’s Pause for Two Questions from the

Audience

Newton’s second law

Mass is a measure of inertia. It’s just a number used to

compare inertias.

Newton’s second law

ΣF = ma

ΣF represents the net force acting on an object.

m represents the mass of an object, which is a numerical measure of its inertia.

a represents the acceleration of the object.

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Let’s Pause for Two Questions from the

Audience

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Mass and Weight

Mass is:Something you go to if you are Catholic.

The amount of “stuff” in an object.

A measure of an object’s inertia.

A force that resists motion.

Weight is:The gravitational force the Earth exerts on an object.

The gravitational force any object exerts on another object.

The same as mass, but with different units.

A good song by The Band

• Mass is a measure of inertia. It is the m that goes into F = ma.

• Weight is the force that gravity exerts on something. Weight is the F in F = ma.

The accelerations of the two objects are the same

For the large object:F = ma

Weight of large object = (mass of large object)(acceleration of large object)

W = mg

For the small object:

F = maWeight of small object = (mass of small object)(acceleration of small object)

w = mg

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Fgrav =Gm1m2

r2

For an object near the surface of the Earth:

F = maGmEarthmobject

rEarth2 = mobjectaobject

GmEarth mobject

rEarth2 = mobject aobject

GmEarth

rEarth2 = aobject

Thank you!

Let’s Pause for Two Questions from the

Audience

Thanks to our presenter, Dr. Bill Robertson, and

to NSTA Press for sponsoring this program

http://www.elluminate.com

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http://learningcenter.nsta.org

• NASA: Discover the Universe – From Galileo to Today

December 16, 2008

• NSTA Press: Picture-Perfect Science Lessons

December 17, 2008

• FDA: Teach Science Concepts and Inquiry with Food

December 18, 2008

http://learningcenter.nsta.org

National Science Teachers AssociationDr. Francis Q. Eberle, Executive Director

Zipporah Miller, Associate Executive Director Conferences and Programs

Al Byers, Assistant Executive Director e-Learning

LIVE INTERACTIVE LEARNING @ YOUR DESKTOP

NSTA Web SeminarsFlavio Mendez, Senior Director

Jeff Layman, Technical Coordinator