Showing posts with label centripetal force. Show all posts
Showing posts with label centripetal force. Show all posts

20071011

Physics clicker question: circular motion free-body diagrams

Physics 5A, Fall Semester 2007
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Problem 5.38

Students were asked the following clicker questions (Classroom Performance System, einstruction.com) in the middle of their learning cycle:

Use these free-body diagrams for the following questions:


[0.6 participation points.] Which free-body diagram represents a passenger (upside-down) at the top of a vertical loop, traveling fast enough that there is still contact with the seat?

Sections 0906, 0907
(A) : 1 student
(B) : 10 students
(C) : 10 students
(D) : 9 students
(E) : 1 student
(F) : 8 students

Correct answer: (F)
At the top of the circular arc, the net force points inwards (downwards), which is comprised of both the downwards normal force of the seat on the passenger, and the weight force of the Earth on the passenger.

[0.6 participation points.] Which free-body diagram represents a passenger (upside-down) at the top of a vertical loop, traveling just fast enough that there is barely contact with the seat?

Sections 0906, 0907
(A) : 0 students
(B) : 0 students
(C) : 2 students
(D) : 1 student
(E) : 35 student
(F) : 1 student

Correct answer: (E)
At the top of the circular arc, the net force points inwards (downwards), which is comprised only the downwards weight force of the Earth on the passenger.

20071010

Uniform circular motion: wall of death

Rhett "Rotten" Giordano, New Orleans Superdome Bike Expo
http://www.650motorcycles.com/83expoGrinder.jpg

Demonstration of how the (upwards) static friction force prevents the bike from sliding down the "Wall of Death," while the (inwards pointing) normal force provides the net force required for uniform circular motion.

20071009

Uniform circular motion: centripetal net force

Li Wei, liweiart.com
047-01, "Life in the high I" (detail)
Beijing July 1, 2004

Demonstration of the inward (centripetal) net force required for uniform circular motion.

20070719

Batgirl centrifuge

Batman #129 (1960), cover by Sheldon Moldoff and Ira Schnapp
Courtesy Mike's Amazing World of DC Comics

Physics 8A learning goal Q4.5

For the villain's sake, let's hope that Batgirl doesn't start get nauseous while still on that thing...

20070530

"Centrifugal absorption reciprocating" van


Centrifugal Absorption Reciprocating
Originally uploaded by Frauenfelder.

Physics 8A learning goal M2.1

The wondrous incongruity of it all!