Class_Notes

October 20, 1998

Announcements

• Apology for snafu last week but I'm proud of the reports of what happened at most of the sites of the mentors and of the teachers taking the class. Thanks for making the best of the situation.
• WVSTA teachers should all be proud of the progress in Science in the State increase of teacher participation from 60 in the 80s to over 700 in the 90s. Thanks to Phyllis Barnhart and all of those who helped to bring teachers together.
• Thanks to all of you who prepared presentations which were excellent I wish I had known of the expertise that many of you have been hiding and that you would speak up to share such gems with the rest of the teachers. In fact, I would like some help in making the WEB a means of sharing such classroom activities. If you can create HTML files that I could upload easily without typing or at least Word files that I can change to HTML or even electronic files that I can convert to Word etc.
• Test Information should be available at 7 am Wednesday morning on Topclass. Make sure you don't hit the enter key which does submit what you have done and locks you out. And don't exceed the one-hour time limit; log out and log back in or print out the test, log out, determine the answers you want to feed in, then log back in.
• One suggestion made by the mentors at Snowshoe. I'll pause at times to give you time to reflect and discuss locally and maybe let me know what isn't making sense.

Let's first review kinematics then look at the posted sample test then at keys to the test.

TWO BASIC CONCEPTS

V = DX/Dt and a = DV/Dt

Where

X = Position Along the Path of Motion.

V = Velocity Along the Path of Motion.

a = Acceleration

apath changes magnitude of V.... slope of graph of v vs t.

aperp changes direction of V.... aperp = V^2 / R

Ways to picture motion.

Motion diagrams.... dots along the path

Graphs... position - time..... velocity - time

Vectors

Equations

Samples and how to think

Motion Diagram... Constant acceleration pattern

Velocity pattern... 0, V, 2V, 3V, 4V, etc.... a = DV/Dt

Position pattern .........Intervals X, 3X, 5X, 7X

Total X, 4X, 9X, 16X

Putting same information in a Graph

Velocity Time Graph... slope: a = DV/Dt

Area: DX = V Dt

Position Time Graph... slope: V = DX/Dt

Analyzing motion with vectors of Velocity, Acceleration

Interactive Physics samples of motion... apath, aperp, v

Sample Test Questions

Discussion of Test

Changing from Kinematics to Dynamics... introduce mass, m, of object that is moving with velocity, V, and has acceleration, a.

Interactive Physics... the Pendulum.

Multiplying V and a vectors by mass m

m V is called "motion" or momentum

m a is called "net force"... F = ma

Newton stated that the net external force on a body causes acceleration of the body

a = DV/Dt

m a = D(mV)/Dt

F = m a = D(mV)/Dt

Interactive Physics with Pendulum... adding Ftotal.

But what are real forces.

Non-contact forces.... Gravity F = G M m/r^2 = m g

Contact force... String

Add Gravity and String forces to Pendulum

So where did Ftotal come from... diagonal of parallelogram.

Other types of forces.

Interactive Physics ... block on surface.