Angular vs. linear motion
Difference between w and vT.
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
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2. Imagine a Compact Disc spinning. Which part of
the CD has a larger w? Remember: w 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
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3. Imagine a Compact Disc spinning. Which part of
the CD has a larger linear (tangential) velocity vT?
Remember vT 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
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Answers
1. same – all solid objects spin this way. Nonsolid 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 w, 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. vT = rw. w is the
same, but r is not.
Conceptual question 7-15. Is it possible to move in
a circular path that has tangential acceleration, but
not centripetal acceleration?
1. Yes
2. No
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Conceptual question 7-15. Is it possible to move in
a circular path that has centripetal acceleration,
but not tangential acceleration?
1. Yes
2. No
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Problem 8-6: what angle?
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