Coins falling in water

Journal of Fluid Mechanics
Volume 742 / March 2014, pp 243-253
Cambridge University Press
DOI: http://dx.doi.org/10.1017/jfm.2014.6

Luke Heisinger, Paul Newton and Eva Kanso

University of Southern California, Los Angeles, CA 90089, USA

Abstract

When a coin falls in water, its trajectory is one of four types, determined by its dimensionless moment of inertia I∗ and Reynolds number Re: (A) steady; (B) fluttering; (C) chaotic; or (D) tumbling. The dynamics induced by the interaction of the water with the surface of the coin, however, makes the exact landing site difficult to predict a priori. Here, we describe a carefully designed experiment in which a coin is dropped repeatedly in water to determine the probability density functions (p.d.f.s) associated with the landing positions for each of the four trajectory types, all of which are radially symmetric about the centre drop-line. In the case of the steady mode, the p.d.f. is approximately Gaussian distributed with small variances, indicating that the coin is most likely to land at the centre, right below the point from which it is dropped. For the other falling modes, the centre is one of the least likely landing sites. Indeed, the p.d.f.s of the fluttering, chaotic and tumbling modes are characterized by a ‘dip’ around the centre. In the tumbling mode, the p.d.f. is a ring configuration about the centreline whereas in the chaotic mode, the p.d.f. is generally a broadband distribution spread out radially symmetrically about the centreline. For the steady and fluttering modes, the coin never flips, so the coin lands with the same side up as when it was dropped. The probability of heads or tails is close to 0.5 for the chaotic mode and, in the case of the tumbling mode, the probability of heads or tails is based on the height of the drop which determines whether the coin flips an even or odd number of times during descent.

The original version of this article was published with the incorrect order of authors. A notice detailing this has been published and the error rectified in the online and print PDF and HTML copies.

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9179743

The Greedy Bastard’s Guide to Business

Journal of Macromarketing
December 2013 vol. 33 no. 4 369-385
doi: 10.1177/0276146713491435

Morris B. Holbrook, W. T. Dillard Professor Emeritus of Marketing, Graduate School of Business, Columbia University, 140 Riverside Drive, #5H, New York, NY 10024, USA

Abstract

Greedy Bastards, eager to achieve success in the business world, need helpful advice on steps toward climbing to the top. Drawing on the author’s 35-plus years of experience in teaching MBAs, the present treatise offers tips in the form of a self-help tutorial intended as an inspirational guide. In that spirit, the discussion covers pertinent aspects of business education; impression management (Dre$$ for $ucce$$); tips from travel services; ethics; borderline-legal corruption; unintended benefits such as obesity, traffic, cell phones, and impacts on popular culture – culminating in a Greedy Bastard’s Honor Roll of Civic Achievements.

http://jmk.sagepub.com/content/33/4/369.abstract

Commercial Features of Placebo and Therapeutic Efficacy

JAMA The Journal of the American Medical Association
March 5, 2008; 299(9): 1016-1017
doi:10.1001/jama.299.9.1016

Rebecca L. Waber, BS
Massachusetts Institute of Technology
Cambridge, Massachusetts

Baba Shiv, PhD
Stanford University
Stanford, California

Ziv Carmon, PhD
INSEAD
Singapore

Dan Ariely, PhD
Massachusetts Institute of Technology

To the Editor:
It is possible that the therapeutic efficacy of medications is affected by commercial features such as lower prices. Because such features influence patients’ expectations, they may play an unrecognized therapeutic role by influencing the efficacy of medical therapies, especially in conditions associated with strong placebo responses. To investigate this possibility, we studied the effect of price on analgesic response to placebo pills.

Author Contributions:
Dr Ariely had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Waber, Shiv, Carmon, Ariely.
Acquisition of data: Waber.
Analysis and interpretation of data: Waber, Ariely.
Drafting of the manuscript: Waber, Shiv, Ariely.
Critical revision of the manuscript for important intellectual content: Waber, Shiv, Carmon, Ariely.
Statistical analysis: Waber, Ariely.
Obtained funding: Ariely.
Administrative, technical, or material support: Waber.
Study supervision: Ariely.

Financial Disclosures:
None reported.

Additional Contributions:
Taya Leary, MS, Tom Pernikoff, BS, and John Keefe, BS, all with the Massachusetts Instituteof Technology at the time of this study, provided assistance in data collection. Mr Keefe received compensation for this role. Andrew Lippman, PhD, Massachusetts Institute of Technology, provided logistical support and Mark Vangel, PhD, Massachusetts General Hospital, provided statistical assistance. Neither received compensation for these roles.

http://jama.jamanetwork.com/article.aspx?articleid=181562

Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrus?

Evolution and Human Behavior
Volume 28, Issue 6, November 2007, Pages 375–381

Geoffrey Miller, Joshua M. Tybur, Brent D. Jordan

Department of Psychology, University of New Mexico, Albuquerque, NM 87131, USA

Abstract

To see whether estrus was really “lost” during human evolution (as researchers often claim), we examined ovulatory cycle effects on tip earnings by professional lap dancers working in gentlemen's clubs. Eighteen dancers recorded their menstrual periods, work shifts, and tip earnings for 60 days on a study web site. A mixed-model analysis of 296 work shifts (representing about 5300 lap dances) showed an interaction between cycle phase and hormonal contraception use. Normally cycling participants earned about US$335 per 5-h shift during estrus, US$260 per shift during the luteal phase, and US$185 per shift during menstruation. By contrast, participants using contraceptive pills showed no estrous earnings peak. These results constitute the first direct economic evidence for the existence and importance of estrus in contemporary human females, in a real-world work setting. These results have clear implications for human evolution, sexuality, and economics.

Keywords

Estrus; Female sexuality; Behavioral economics; Sexual service industries; Hormonal contraception

http://www.sciencedirect.com/science/article/pii/S1090513807000694