__Free Body Diagrams__:

Day 1: Two videos describing the role of vectors: Vectors: Forces, momentum, Vectors: Energy and Kinematics

1. Readings

- 3.0-3.3 Kinematics and vectors
- 4.3 Newton’s Second Law of Motion: Concept of a System
- 7.1 Work, the Scientific Definition
- Inelastic Collisions in 2 dimensions: see example at http://www.ux1.eiu.edu/~cfadd/1150/07Mom/Inelastic.html and http://www.batesville.k12.in.us/physics/apphynet/Dynamics/Collisions/inelastic_2d.htm

During class, we’ll do example of work with vectors

W=dE=F*x (a dot product), *the vector SUM of* F = m*a.

Day 2: The Free Body Diagram, and Dynamics Problems

Bozeman Science FBDs

The Elevator Dynamics Problem

Read chapter 3.4-4.7 about dynamics

The *vector sum of the* Forces = mass * acceleration.

What is equilibrium? How do we find the resultant force? We introduce the “dynamics protocol” (Quiz on this tomorrow):

“The Protocol for Dynamics”:

0) Identify that this problem is about forces => It’s a dynamics problem

1) “oh shit, I don’t know anything”… there’s no formula for a dynamics problem!

2) “but I do know that (vector sum) F = ma”

3) I can draw a force (free body) diagram labeling all the forces at the point of action.

4) I can ask myself “is it in equilibrium?”

=> yes – then the sum of the forces is zero and the vectors must close on themselves

=> no – then I ask another very important question, “which way is it accelerating?” and know that the forces must add to be in the same direction as the acceleration.

5) Then show graphically how the force vectors add to provide a resultant force (the net force) in the same direction as the acceleration.

Day 3:

Read chapter 3.4-4.7 about dynamics

Before Class, please read solutions to the problem set:

PS2_2

PS2_2e

PS2_3

PS2_4

PS2_5

During class: Quiz on Protocol for Dynamics,

What is an equal and opposite force?

Day 4:

Springs, Hook’s Law__Before Class:__

See video: *Springs!*

and another video on Estimating Trigonometry

and another video on Adding Forces Graphically

During Class: Quiz on Newton’s 3rd law and improvements

formulas: gravitational potential energy, spring potential energy Hook’s Law.