Physics Honors/AP 1 and 2

Homework

# Physics 6: 8-10 Power and Non-Conservative Forces

## Homework

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 6: Sections 8-10

##### Study Points
• Section 6.8: If a system is isolated and neither matter nor energy can cross its boundaries, then the total amount of energy inside the system cannot be increased or decreased; it can only change form. [Later we will come back to the issue that every such metamorphosis involves the change of some energy into energy that can no longer do work.]
• Section 6.9: We determine the amount of friction acting by looking at the difference between the work done by conservative forces and the actual change in energy of a given system. One way of explaining this is to say that the difference between the ideal predicted by conservative forces and the real is the fudge factor, friction.
• Section 6.10: Power is a new concept, which we define as the rate at which work is done, P = W/t.

### Key Equations

• In any conservative force situation (no non-conservative forces acting):

This is a state change.

• Power

### Web Lecture

Read the following weblecture before chat: Power

### Study Activity

Experiment with different masses and spring constants to determine how these affect spring behavior.

Physics simulation Java Applets are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.

### Chat Preparation Activities

• Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

### Chapter Quiz

• Required: Complete the Mastery exercise with a passing score of 85% or better.
• Go to the Moodle and take the quiz for this chat session to see how much you already know about astronomy!

### Lab Work

If you want lab credit for this course, you must complete at least 12 labs (honors course) or 18 labs (AP students). One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!

• Lab Instructions: Conduct the Atwood's Machine experiment to determine the friction of a pulley.