Brain Teaser Challenge Solution - May 2008 Butch Shadwell
If you recall, in the last BTC I recounted a discussion I had many years ago. “…in a discussion among some physicists about a laser weapon. There was some debate about whether it should be a high energy beam or a high power one in order to successfully shoot down a missile in flight. I’d like to hear what you think.”
I mentioned that the discussion was complicated by the fact that there were some engineers in the group. This stems from the fact that for a physicist the energy of a wave or particle beam refers to its wavelength. Higher energy photons have a shorter wavelength. Of course for the engineers, energy was simply the integral of the power over time.
Even when we settle on the engineering terms, the answer is still not necessarily obvious. You can impart the same amount of energy to the surface of the target with a low power photon beam as you can with a high power photon beam by letting the low power beam run longer (integral over time right). However, if the objective is to damage the target by heating the skin to the melting point, then the rate of heat dissipation in the target skin is a key factor. This establishes a lower limit on the power level of the photon beam, i.e. – the beam must impart heating energy faster than it is dissipated on the surface of the target. Finally, since it is very difficult to keep the laser accurately focused on a particular point on a fast moving target, then it would seem that you must have a very high power beam to have a chance of getting enough energy into the target to do any harm in the short time frames available. But I bet you already knew that.
Brain Teaser Challenge – June 2008 Butch Shadwell
As I am writing this piece, the Fourth of July is just around the corner. Everyone looks forward to the picnics, pyrotechnics, and patriotism. This is definitely one of the happier holidays on the American calendar, the date that the Continental Congress adopted our Declaration of Independence, in Philadelphia. Eventually, there were 56 signers of this document. These brave men risked everything, including their very lives, to do what they believed was the honest and right thing. I hope our congress men and women of today will reflect on these predecessors during this holiday.
With gas prices going through the roof, holiday travel can be very expensive. As a large part of our energy consumption is for cars, it is important that we understand how to get better gas mileage. Most cars have two or three pedals on the floor. This month I am asking you to tell me which one is the cause of the most loss of fuel economy. Most folks get this one wrong.
Have a great Independence Day, … if you are in the USA that is.
Reply to Butch Shadwell at b.shadwell@ieee.org (email), 904-223-4510 (fax), 904-223-4465 (v), 3308 Queen Palm Dr., Jacksonville, FL 32250-2328. (http://www.shadtechserv.com) The names of correct respondents may be mentioned in the solution column.
Brain
Teaser Challenge by Butch Shadwell
