Mechanics Week 6

Week 6 - Becoming Quantitative with Energy

In Class Activity Plan (Word, Pdf)

Week Six: Becoming Quantitative with Energy

120 min Investigating Energy Conservation (Word, Pdf)

PURPOSE: Introduce equations for Eg and Ek, opportunity to design experiment

Teaching Notes:

  • You should whiteboard after the first page (making pie charts).

    • Goals here will be to push them towards the answers to the questions on page 2.

    • Suggest energy at the top should be proportional to both mass and height.

  • For many students this will be the first time they have ever had to design their own experiment. So this lab will both take a long time, and be difficult for some students.

    • The proposal must have a model associated with it, and must identify what measures are going to be made and how the data is going to be analyzed.

    • Also, the teacher must be very good at evaluating experiments on the fly. They may think of things that would work, but we haven’t thought of before.

  • Possible experiments:

    • Drop the ball from different heights and record the speed at the bottom. They can then make a graph of EIg and Ek and get a linear fit.

    • Also a possibility of rolling things on rails and measuring speeds.

20 min Whiteboard – Investigating Energy Conservation

PURPOSE: Share experimental designs and results for equations for Eg and Ek

Video Example:

  1. What did you learn?

  2. What rules can you make?

  3. What questions do you still have?

45 min Board Meeting

PURPOSE: Compare experimental designs and results for Eg and Ek, reach consensus about how to calculate Energies.

Video Examples:

  • Need to define system (Schema)

  • Use pie charts to help you determine what needs to be measured

  • Strategy 1

    • EIgo – EIgf

    • Plot Ek vs. v

    • Fit a curve in Excel

  • Strategy 2

    • EIgo = magh

    • Ekf = m (Δv/Δt)(½ag(Δt²))

    • Ekf = m (Δv/Δt)(½(Δv/Δt)(Δt²))

    • Ek = ½mv²

    • Must be supported by data!

  • Energy Pie Charts are a representation of the Equation of Everything (energy conservation)

20 min Whiteboard - 1-d problem using both kinematics and energy conservation

PURPOSE: Compare and contrast strategies for making calculations on constant a model using kinematics and energy

Problem: Cubs fan throws his hat straight into the air at 7m/s.

10 min Board Meeting

PURPOSE: Show how basic constant a models obey energy conservation and give same results.

Emphasize energy as an easy approach that works well in some situations.

60 min Whiteboard - Redo 2-d problems using energy &/or additional problems

Energy Pie Chart Problems (Word, Pdf)

Energy Problems for Practice (Word, Pdf)

Video Examples:

Note: These are often done, but not discussed in a board meeting since they have done them previously.