# Week 3 Vectors

This week, we look at vectors, and forces and how they related to acceleration, energy, and momentum

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

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

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:
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.