Angular vs. linear motion Difference between  and v T. These questions are based on a previous student’s questions during class.

1. Imagine a Compact Disc spinning. Which part of the CD completes one revolution in less time? 1.Part near the inside (small radius) 2.Part near the outside (large radius) 3.They are both the same

2. Imagine a Compact Disc spinning. Which part of the CD has a larger  ? Remember:  has units such as revolutions/minute. 1.Part near the inside (small radius) 2.Part near the outside (large radius) 3.They are both the same

3. Imagine a Compact Disc spinning. Which part of the CD has a larger linear (tangential) velocity v T ? Remember v T has units such as meters/second. 1.Part near the inside (small radius) 2.Part near the outside (large radius) 3.They are both the same

Answers 1.same – all solid objects spin this way. Non- solid objects (e.g. gas planets, stars) can have different spin rates at different locations. But solid objects cannot. 2.same. Similar to #1. 3.outside. Everyplace has the same , and therefore takes the same time for one complete spin. But because the outside has a larger radius, it covers more distance in 1 revolution than an inner part. v T = r .  is the same, but r is not.

Conceptual question Is it possible to move in a circular path that has tangential acceleration, but not centripetal acceleration? 1.Yes 2.No

Conceptual question Is it possible to move in a circular path that has centripetal acceleration, but not tangential acceleration? 1.Yes 2.No

Problem 8-6: what angle?