Motion System Design
Fun with Fundamentals: Problem 161

Fun with Fundamentals: Problem 161

Best Rate and Solution to Problem 160. A mound of dirt by any other name can also smell as sweet, as this month's problem by James White of Henderson, Ky., demonstrates

Base rate

Problem 161 — A mound of dirt by any other name can also smell as sweet, as this month’s problem by James White of Henderson, Ky., demonstrates.

“Mr. Wurme, do you have anything further to add to your testimony?” The case of Lee Key Hydraulic Co. vs. Finagel J. Wurme was now in its fifth week. The case centered on the company’s on-site landfill, which had overflowed into a nearby river. Eight years ago, Wurme had been in charge of digging the landfill and assuring it could handle Lee Key’s needs for the next ten years. Wurme contended it was Lucius Bluff’s inept management of waste disposal that caused the mishap.

Wurme’s design of the landfill called for a base layer covered by a top layer. The base layer is composed of filter cake (FC) and bottom ash (BA); and the top layer, FC and fly ash (FA).

“Your honor, I present the following statement that proves the landfill should have been able to last us for ten years,” snipped Wurme. “When I made the calculations for this landfill eight years ago, it could have lasted us for ten years easily.”

Wurme’s statement gave the following information:
• 1,750,000 yd3 had been the total space available for both layers.
• 387,000 yd3 was the space available for the top layer.
• Lee Key produces FC at a rate of 288,000 tons per year. FC has a density of 87.5 lb/ft3.
• The company produces 30,000 tons per year of BA. It has a density of 60.0 lb/ft3.
• Of the space available for top layer, 356,122 tons were allotted for FC.
• The production rate of FA is inconsequential, since any amount over the landfill’s capacity is sold.

Ladies and gentlemen of the readership, you have the facts before you. Given the above yearly production rates and capacities of the landfill, for how many years could the landfill have been used? Is Wurme guilty or innocent of an EPA violation?

Remember, the FC goes to both base and top layer.

Technical consultant: Jack Couillard, Menasha, Wis.

Solution to last month’s problem 160 — You know what your leverage is if you answered 80 ft. Here are the pivotal forces:

Divide the problem into two parts, and let F1 be the force on the rope exiting the large pulley and F2, the 10-lb upward force on the long end of the lever. First, solve for F1:

F1 = w × Ra

w = weight of water, given as 833.6 lb (8.336 lb/gal 3100 gal).

Ra = mechanical advantage of pulley system. In this case it is the small pulley diameter divided by the large, or 4/25.


F1 = 833.6 lb × 4/25 = 133.4 lb

Now, let:

s1 = length of short end of lever, given as 6 ft.

s2 = length of long end of lever, ft. F1s1 = F2s2

Solving for s2:

Thanks to Wurme, Bluff’s presentation was all wet!

Contest winner — Congratulations to Hugh Wesler of Springfield, Mass. who won our March contest by having his name drawn from the 136 contestants who answered 137 ft. for that month. Total responses were 163. A TI-68 calculator is in the mail to him.

The TI-68 Advanced Scientific Calculator by Texas Instruments can solve five simultaneous equations with real and complex coefficients and has 40 number functions that can be used in both the rectangular and polar coordinate systems. Other functions include formula programming, integration, and polynomial root finding. The calculator also features a lastequation replay function that lets you double-check your work.

To enter the contest, send your answer on a postcard or letter to POWER TRANSMISSION DESIGN, 1100 Superior Ave., Cleveland, OH 44114-2543.

You can also receive a TI-68 and credit in the magazine if you send in an original problem with solution, and we publish it.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.