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Re: rotating space station



You're not stupid. You can try some of this stuff on a merry-go-round (MGR)
at your local park or playground. Stand or sit on the (MGR) with you back
facing outward. (In either case, brace yourself well with your legs,
because you want to have your hands free.) Take a ball (e.g. a soccer ball)
and get someone to push you at roughly a constant angular velocity. In this
position you would be approximating lying on the "floor" of the space
station. If the answer manual to your text is correct, you ought to be able
to throw the ball "upward" (away from you) and then it would come back
"down" and you could catch it. Ha! Good luck!

Even more fun. Get on the MGR with 3 other people spaced equally apart.
Get spinning, and try to play pitch and catch with the soccer ball. The
apparent path of the ball is bizarre. Eventually you learn where you have
to throw the ball to make it go to a specific person. You have to be
careful both as a thrower and as a catcher. You may initially think that
Ted threw the ball to Sally, and about the time you're thinking that it
comes and smacks you in the side of your face.

Annually I would take my physics class to the playground for a full period
of playing ball on the MGR. Unfortunately I am one of those persons who
gets sick on MGR. After class I would usually vomit and I would feel
nauseous for the rest of the day. I figured the physics was so cool that it
was worth it. But now I'm older and I look back and think, "now that was
really stupid."


Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817

Carl Mungan said:

Serway "Principles of Physics" 2nd ed. Chapter 5 Question 6:

Consider a rotating space station spinning with just the right speed
such that the centripetal acceleration on the inner surface is g.
Thus astronauts standing on this inner surface would feel pressed to
the surface as if they were pressed into the floor because of Earth's
gravitational force Suppose an astronaut in this station holds a
ball above her head and "drops" it to the floor. Will the ball fall
just like it would on the Earth?

Detailed (excuse my sarcasm) answer given in the Solutions Manual: Yes.

I think that answer is wrong. From the point of view of an inertial
observer, the "dropped" ball will continue horizontally at a constant
speed equal to the tangential speed of the space station until it
hits the floor. Meanwhile the space station rotates and hence the
component of the astronaut's velocity in the original horizontal
direction decreases. Thus it seems to me that the ball should hit the
floor ahead of the astronaut, and not right at her feet like on Earth.

Am I being stupid? Carl
--
Dr. Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Annapolis, MD 21402-5026 mailto:mungan@usna.edu
http://physics.usna.edu/physics/faculty/mungan/