Physics Core/AP 1 and 2

Homework

Physics 8: 6-9 Rotational Kinetic Energy

Homework

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 8: 6-9

Study Points
• 8.7: We've covered the rotational equivalents of kinematics and dynamics. Now we just do the same thing with kinetic energy and angular momentum, using angular velocity and moment of inertia in the same relationships as we used linear velocity and mass. Rotational kinetic energy = 1/2 I ω2. To use this, we have to recognize that something can have rotational kinetic energy if it is spinning or rolling and translational kinetic energy if its center of mass is changing position. The two can be separately calculated.
• 8.8: Angular momentum is conserved, just like linear momentum. If no outside torque acts on an object to change its rotational speed or direction, its angular moment remains unchanged. Note that a linear force can act on the object to speed up or slow down or change its linear velocity without changing the angular motion of the object.
• 8.9: The right hand rule tells us the direction of the result of angular momentum and torque calculations. This is a vector at right angles (out of the plane) in which the original vectors lie. To figure the direction of angular momentum, put your wrist at the center of rotation, point your fingers out along the radius, then curl them in the direction of rotation. Extend the thumb in a hitch-hiking gesture. The thumb now points in the direction of the angular momentum vector.

Key Equations

Linear Angular
KEtranslational = ½mv2 KErotational = ½Iω2
= m = Iω̅

Web Lecture

Read the following weblecture before chat: Inertia, Acceleration, and Force

Study Activity

Use the physics simulation ==>HERE<== to experiment with angular momentum.

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!