# High school physics teacher seeking slide rules

1. Sep 5, 2012

### misterpugsly

Hiya folks,

In an effort to get the students in my Advanced Physics class to rely less on calculators and to develop their math skills, I am going to give them the option of using slide rules this year. I am offering them a small bonus on tests if they use slide rules instead of calculators. I have nothing against calculators, but slide rules force students to do some of the work manually, which I believe will be a good thing. The trouble I am having having is finding enough slide rules. Most sites that sell them market them as collectibles, with prices often ranging into the hundreds of dollars. I found some on Ebay, but the ones in my price range (I am doing this out-of-pocket) are in poor shape. Does anyone know somewhere I can buy inexpensive new slide rules? Thinkgeek used to sell them, but I don't see them on their site any more (and they have not yet replied to the two emails I have sent).

Any help on this would be appreciated.

Tom

2. Sep 6, 2012

### Woopydalan

They aren't going to use slide rulers ever again, seems like a waste of time and money to me

3. Sep 6, 2012

Staff Emeritus
There were a large number of cheap plastic pocket rules by Pickett made in the early to mid-70's and sold in drugstores. Every once in a while a crate of them is discovered and will be sold to a place like American Science and Surplus. You need to keep an eye out for them, because otherwise you are buying "collectibles". I bought a dozen of them for $50 a few years back. These Picketts are not the greatest, but they are slide rules. I have a Scientific Instruments 1520, which is a very nice bamboo rule with a plastic cursor. These run$50-75 on Ebay when you can find them, so you can see the cost differential.

4. Sep 6, 2012

### Aero51

Why don't you just use numbers that don't require extensive amounts of time to manipulate. IE don't let your initial velocity equal 57.002958..

5. Sep 6, 2012

### turbo

K+E made some cheapie plastic slide rules, too. Many of us over 40 years ago couldn't afford the bamboo and ivory models.

6. Sep 7, 2012

### misterpugsly

As far as why I bother, let me quote the wiki article on slide rules:

"The spatial, manual operation of slide rules cultivates in the user an intuition for numerical relationships and scale that people who have used only digital calculators often lack.[21] Since users must explicitly note the order of magnitude at each step in order to interpret the results, they are less likely to make extreme calculation errors; users are forced to use common sense and an understanding of the subject as they calculate. Since order of magnitude gets the greatest prominence when using a slide rule, and precision is limited only to the few digits that are normally useful, users are less likely to make errors of false precision."

It's that "intuition for numerical relationships and scale" that my students lack. Yes, my class is the only one they will probably ever use slide rules for. But if are able to develop their intuition, then they will be less likely to tell me that the Moon orbits the Earth at a distance of 7 m (an actual answer I got before) just because "the calculator said so." They already can use calculators and they can continue to do so - I'm not forcing anyone to use the slide rules. And I never use values like 57.002958 - usually I only use 3 significant digits. It's my students who tend to use long strings of meaningless values, hence the comment in the wiki paragraph above about errors of false precision.

To be honest, I was not inviting a debate, but rather requesting if anyone knew of a source for a particular educational device. Vanadium 50, thanks for the info on American Science and Supply - I checked it out, and while they do not have any, at least you attempted to answer the question I asked.

7. Sep 7, 2012

### BobG

You could try Slide Rule Universe. Their regular prices are higher than what you could find on eBay, but they do have special deals for teachers.

http://www.sphere.bc.ca/test/cheap.html#catalog

Slide rules also nudge the student to focus on relationships rather than just memorizing an equation. You don't just solve x = 6.78 * 3.25. You can also solve 6.78 = 3.25/x or 3.25=6.78/x. What you're solving for can be anywhere in the equation and since you lose a little accuracy everytime you re-index, you learn to intentionally set up your calculations so as to re-index as few times as possible.

There's other subtle little things a person learns. You have greater precision on the left side of the slide rule (up to 4 sig digits) and less on the right side (down to 2 sig digits), there's this initial feeling that you have to be extremely accurate when using numbers on the right side of the slide rule. It takes a while to realize that using a slide rule means a change in domain and an 1/16th of an inch is a 1/16th of inch regardless of whether it's on the left or the right. The only time the side of your slide rule matters is when you're changing back into a numerical domain and actually write down your answer.

It really does change how a person views numbers and calculations in a lot of subtle ways.

And you really could complete quite a few college classes with a slide rule. I took a chemistry class in the 2000's that used a text written by Raymond Chang. You get this feeling he must collect slide rules because every problem is set up to be solved using a slide rule. I completed an Electrical Engineering degree using slide rules almost exclusively (I have quite a few, so I like to try out different ones and the layout of the scales definitely does make a difference in how you approach different problems).

There are some things that are just better done on a modern graphing calculator. One can do Cramer's Law manually, or matrix multiplication manually, but too much of that gets old real quick.

And, for the record, my avatar is an extreme close up of my little pocket Pickett.

Last edited: Sep 7, 2012
8. Sep 7, 2012

### tygerdawg

I think you will be challenged to find a decent supply of decent slide rules. I remember finding a site where this guy discovered and re-sold old inventory hidden in stores (perhaps it is the Slide Rule Universe site, I vaguely recall it was in Vancouver BC Canada). But all the "good" ones were snapped up. I didn't act when necessary.

I understand your concern with students and calculators. At one time I taught some college level introductory engineering classes as an adjunct professor. In an effort to reduce dependency on calculators, I explained to them how to set up and attack a problem "the way engineers do it."

Every homework / test problem should maintain the same structure template:
• Statement of problem
• Given data
• Applicable or pertinent equations
• Required goal, answer, or achievement
• Mathematical derivation & manipulation of equations to produce the desired result, but only in symbolic form...do not plug in numbers
• Only after all of that, plug in numbers and calculate. Points were subtracted if they did not produce the final result in correct number of significant digits.

I was watching students plug numbers into calculators and write down strings of numbers out to 8 decimal places...useless and a waste of time. I told them if they solved the problem symbolically without plugging in numbers, then that was a "B" grade effort right there...IF they followed the correct format template (which made my grading easier). They were shocked, but their grades and efforts improved immediately. And it gave me the opportunity to throw more challenging stuff at them which made them think more analytically.

I also introduced them to an "ancient" method I discovered back in the 70's when I was struggling how to take notes effectively. I recall I purchased a small paperback titled something like "how to use the PIE method" or similar. P-I-E for Principles, Information, Examples (IIRC) and described how to take notes in a clean, structured, organized manner. Suited my twisted brain cells very well and grades immediately improved.

9. May 1, 2013

### gotwals

Tom, have you tried this yet? I have 24 slide rules that I've purchased, and I want to try having science kids use slide rules for the reasons you have suggested. Looking to find others who have tried this and ask them what worked, what didn't.

10. May 1, 2013

### dkotschessaa

You're missing the point, big time. I think it's an awesome idea.

To the OP

I came across this site once about how to build one from scratch. I don't know if that's practical for your purposes (bonus bonus points for building one?) but here it is:

http://www.sphere.bc.ca/test/build.html

11. May 1, 2013

### SteamKing

Staff Emeritus
Dude! Physical slide rules are so TwenCen! You can equip your class with a 21st Century Slide Rule App!

No slide rule protector to rat you out! You don't have to worry about losing it or breaking it. If this app don't slide your rule, I'm sure there are others somewhere on the web.

Last edited by a moderator: May 6, 2017
12. May 2, 2013

### dkotschessaa

Do you have any further info on this? I am desperately in need of a better method of note taking. A google search isn't turning up much. An amazon search turns up microwaves. If it's not too much trouble, and if you have any info, could you either PM me with some details or we could start a thread about it? I don't want to hijack this thread...

-Dave K

13. May 2, 2013

### dkotschessaa

To reiterate the fact that I think it's a great idea.... I am currently reading a book about "e" right now. (Eli Maor: e: The Story of a Number) and it made me realize that I have a big gap with regards to my knowledge of logarithms. (I couldn't even spell "logarithm" without spell check, if that gives a clue.)

The Slide Rule Users of Yore (like my father) seem to have an intuitive grasp of logarithms, of which I am at times envious. This would allow, I would think, a better understanding of the exponential function, a vitally important key to calculus and differential equations.

Even if they never use it again, it is one of the things your students will likely never forget about your class. I hope you have sucess with it.

-Dave K

14. May 2, 2013

### marcusl

I'm not one to dissuade you, but I also don't think that slide rules really develop useful skills--and I speak with experience. I was a senior in college when I first used a calculator. I had a beautiful K+E one with a zillion scales, and routinely achieved accuracy of 3 significant digits. The physics dept. had purchased an HP 45 calculator and bolted it to a table in the physics library. There was always a long line waiting to use it.

I think it is more useful to be able to solve problems approximately, and to be able to estimate. We were often encouraged to work this way on in-class tests. Numbers like pi, e, and c approximate to 3. Other numbers are rounded off. It is easy to come within 15% of the exact answer this way, and it develops a true feel for numbers and especially for getting the correct order of magnitude. (It's also handy for calculating price per pound at the market and miles per gallon in one's head). These are skills that are useful all through life.

I used to work with my own children to develop these skills when they were in middle and high school, with no very apparent enthusiasm on their part--until my oldest started college. Following a freshman physics test, he called and told me that he worked a problem on his calculator and knew that he'd made an error because he had estimated the answer first, and the calculator was orders of magnitude off! That call made it all worthwhile.

15. Feb 5, 2016

### edu500ac

I don't know whether you have found slide rules for sale. If not, a friend manufactured a few slide rules for my students at a cost of 10 dollars each. He uses a laser to cut the scales. If you are still interrested in slide rules, let me know. My email is edu500ac@gmail.com

16. Feb 5, 2016

### mpresic

Bravo. I had Pickett slide rules in the 70's and went to college with one. The first semester I got and SR-50 calculator. (Maybe the SR stood for slide rule as it was the first calculator that could do everything my log-log slide rule could. Now with high speed computing everywhere, I would not be surprised if kids thought slide rules were cool. It is not all about speed and ease of use. My nieces sill knit, even though a power loom could knit faster.
The slide rule allows you to see a continuum of numbers at once. (talk about parallel processing). I grant you this "advantage" may (possibly) only be realized as a subconscious level, yet it is unlikely that this experience is meaningless.

17. Aug 31, 2016

### Dan Chang

I have three slide rules that I could donate to your class if you still would like them. One is a full size Post Versalog and the other a pocket 6" Versalog. The third is a full size Aristo. Maybe if you post a request here you could generate enough to supply your class, they certainly don't need to be identical. If you still need them send me an e-mail at dpchang@ucdavis.edu. I probably have an old HP calculator lying around somewhere, I think an HP-15.

18. Sep 1, 2016

### mpresic

I actually do not teach. I just think it would be good if teachers would make them available for curious students to learn. As for the HP-15, I think it was the best pocket calculator ever made, for it's size and use. I wish HP would reissue the item at a price around 100-200 dollars. The reissue price was much higher. My HP-15 LED's died about 10 years ago. Many of my friends told me theirs quit at about 30 years. If you still have one that works, I would hang on to it, you're lucky.