AMTA Training Mechanics Day 7

Key Activities:

· Beware the common misconception that when two disparate objects interact the forces are disparate.

· The lab practicum is a mass hanging down with a horizontal thread deflecting the hanging wire.

· We emphasized today the importance of defining a useful system, can simplify analysis in some cases (half-Atwood machine, full Atwood machine)

· We found MKS representation of Newton based on comparing the models we got from our experiments.

· We introduced friction force, hypothesized some model characteristics.

· We noticed in experiment that there was a difference between maximum static friction force and kinetic friction force.

· We calculated coefficient of sliding friction for cork on table top.

Day 7

Tuesday, June 23, 2015

7:37 AM

<<Day 7.wmv>>

Video recording started: 7:37 AM Tuesday, June 23, 2015

Information about Day 7.

Roger and Astronomy Outing Tonight.

Huge Auroras last night, CME was Monday 2pm ET.

Naperville – Plainfield road.

If you aren’t going to be here on Friday

To get free year of membership you need to complete post survey.


There is another worksheet. Equal and opposite forces, little ones on big ones, etc.

Interaction forces. Misconceptions.

Lab practicum is

Be careful with knots they only have tension forces not mass.

Most accurate is usually to measure positions of things.

I-Level will do the same lab with a force-angle protractor

By the end of this unit we have established Newton’s first law and Newton’s 3rd law.

With a net force, we know there is acceleration.

The direction of the net force is the direction of the acceleration

The directoin of the motion is not quite the same as the direction of the acceleration.

Observing the cart with the mass on it.

1. Draw a picture.

Group 5

Prob 8

Video recording started: 11:49 AM Tuesday, June 23, 2015

Video recording started: 11:59 AM Tuesday, June 23, 2015

Video recording started: 12:06 PM Tuesday, June 23, 2015

Video recording started: 12:12 PM Tuesday, June 23, 2015

Introduction to Lab on Friction.

Let’s talk about our friction force.

Video recording started: 1:11 PM Tuesday, June 23, 2015

Talking about the aftermath of the friction experiment (Ffk versus normal force, Ffk versus area)

Group 4 and 5 had felt on tabletop.

Group 6 and 7 had cork on tabletop.

The units cancel out.

Newtons per Newton…

Friction force is about 46-47% of the normal force.

Coefficient of kinetic friction.

Keep surface area constant, but doesn’t depend on the force between the surfaces.

Rubber on Nickel

Steel on Ice…

Coefficient of static friction.

Suggestion is to use the constant velocity carts to drag at a constant velocity.

Tomorrow we talk about 2-D motion.

Honors material.

Friction, Honors Unit 5,

Worksheet #1: 3,6.

Worksheet #2: 2,3,5,6,7







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