**Day 1 (Tuesday):**

**Vectors in the four lenses, proving energy formulas.**

- Student Feedback, THANKS! – please see main page for my summary and response.
- Two videos describing the role of vectors: Vectors: Forces, momentum, Vectors: Energy and Kinematics
- See video on Proving why the kinetic energy formula is correct.
- Check LON-CAPA, “Week 2”
- Please read my summary of your feedback last Friday, on the main webpage.
- PS#1 answers and discussion are posted on the main website. Please have a look.

__I received this communication from Moira (the grader):__

1. If students turn their work in as a group, please tell them to put their first and last names on the first page. This helps me a lot!

2. Students need to explain lens choice more and include more pictures.

3. Conceptual understanding is pretty good. One thing is problem 1 on the PS1. Many students confuse total energy with kinetic energy for talking about which one is conserved or *converted* to heat.

4. I graded the problem set on a 1-3 scale this time rather than letter grades since the homework is for feedback rather than a grade itself. Essentially, A=3, B=2, C=1.

**During Class**

**Hand back PS#1, answers and discussion posted on main website.****Vector diagrams for Dynamics Problems, reviewing the string breaking.****Conserving momentum in the roller coaster problem.****Collect PS#2, review some difficulties**

**Day 2 (Thursday): Springs and potential energy graphs.**

**Before Class**

- See video about:
*Springs!* - See the Ted Talk about Body Position and Success
- See Student Project Video: Measuring Speed of Bullet
- Read about the video project. The link is on the main page.
- Read through problem set #3, posted on the main webpage. Due next Monday.
- 1 problem on LON-Capa for “Springs and Ballistic Pendulum”.
- PS#2 answers and discussion on main class website

**During Class**

**Big Exam #2**– Midterm #1 is NEXT WEEK Thursday. If you hand in formula sheet stapled to your exam, I’ll check your formula sheet and make sure that everything is correct and relevant. Make sure it reflects your understanding.

**Day 3 (Friday): Friction and potential energy graphs** PS #3 is posted

Before Class

– Attention! – We don’t have a friction video. If I don’t get one up Thursday at 1:00, __please read a few pages in your book__.**

- Friction – read section 5.1, but don’t read example 5.1 because we do inclined planes (two dimensional problems) after the first midterm.

Goals:

- Dynamics: Friction is a force = to the product of the coefficient of friction and the normal force between two bodies.
- Dynamics and momentum: Friction acts in the opposite direction of the relative motion of the two bodies exchanging momentum. So say, you are spinning your car’s tires when the light turns green. The tires are moving backwards relative to the ground. This pushes the tires forward and the ground backwards. You can see this especially when some of the road gravel flies backwards.
- Energy: Friction turns kinetic energy or mechanical work into heat energy. In the above example, the tires and road get hot. In drag racing, the cars melt some rubber down on the starting pad by spinning their tires.

- Potential Energy Graphs video
- Some physical work I did at home
- 4 problems on LON-CAPA, “Friction and Potential Energy Diagrams”
- Watch solutions for PS#2: Throwing Box Edu Credit
- Watch solutions for tow truck problem

**During Class**

- Discuss Projects

**Remember** the video project from PS #2 is due on Monday. Please see further description on day 1 of week 4.