# Applications of classical physics

Or… “How I learned the basics of my job in kindergarten”

April 2013

How do you like to go up in a swing,
Up in the air so blue?
Oh, I do think it the pleasantest thing
Ever a child can do!
(Robert Louis Stevenson, in A Child's Garden of Verses)

How better to learn the physical principles that we depend on daily in our technical lives - designing, maintaining, and operating the complex machinery of industry - than through the experience of play as a child?

Principles developed through experience

1. The playground swing - two ways of "pumping"
1. The standing pump, moving the mass of the body closer or farther from the axis of rotation of a pendulum at the appropriate time in the swinging motion. Another example is the skater moving from a slow to faster spin by pulling arms close to body.
2. The sitting pump, using the principles of angular momentum to amplify the swing by rotating the body back and forth during the cycle.
2. In the lingo of the physicist, the standing pump in a playground swing is an example of a parametric oscillator. The sitting pump is an example of a driven oscillator.

3. Fluid flow - the garden hose and sprinkler

The garden hose with a variable nozzle on the end lets us experience Newton's third law. When the nozzle is set for the narrowest spray, you can feel that law - for every action there is an equal and opposite reaction. The force of the water leaving the nozzle at high speed in a long-reaching spray is matched by that of the hose and nozzle pushing back against your hand.

If you have ever added a length of hose in order to spray water in a distant corner of the yard, you might have noticed that the water didn't jet as far from the nozzle. The pressure is reduced because of friction of the water in the longer hose. Technicians experienced in fluid mechanics refer to this reduced pressure as "head loss." There is a similar effect in air ducts in a heating system, although in a different fluid.

Running through the jets from a rotating sprinkler on a hot summer day exposes us to Newton's third law expressed in another way. The water jetting from the three-angled pinwheel arms of a sprinkler causes the pinwheel to rotate.

4. A little red wagon and a ball

Richard Feynman, Nobel Prize winner for his work in quantum physics, told of his childhood fascination with a ball in his wagon.

When he pulled the wagon forward, the ball appeared to roll to the back. When he stopped, the ball rolled forward. He eventually figured out that in the first case, the ball never really went backward when compared to the sidewalk; it only looked that way with respect to the wagon. But it did roll forward when the wagon stopped.

These observations perfectly illustrate Newton's first law, that an object at rest (the ball in the beginning) tends to stay at rest. An object in motion (the ball at the back of the moving wagon) tends to stay in motion as the wagon comes to a stop.

5. The flying hand

I learned some basics of aerodynamics riding in the back seat of a car on a hot summer day. Our car wasn't air-conditioned, so the window was open. I enjoyed sticking my hand out the window, holding it flat as I rotated it in the wind and noting how it was pulled up or down depending on the angle of my hand against the relative wind.

There are other examples, I'm sure. How many of you can trace your understanding of elements of your work in industry to some basic observations you made in your youth, that led to an interest in, and better understanding of, the processes with which you deal every day?

One-meter drop test at Fluke's Product Evaluation and Testing Laboratory. For the product it's not the fall that hurts, it's the stop.

Rugged test tools and acceleration of gravity

At Fluke I have enjoyed watching test engineers dropping new meters and other tools from six feet onto various floor materials from wood to concrete, sometimes making adjustments to their designs, until the product survived this rather harsh treatment. In 1994, one tool I worked with was dropped over twelve times, and the first component that failed was one of the four alkaline batteries that powered it. When the battery was replaced, the meter operated perfectly.

I wonder at times whether these engineers experienced the breakage of one of their toys years ago as the result of a fall. If so, they have certainly taken the message to heart and gone overboard to make sure you don't experience the disappointment that they felt then, when your meter slips from your grasp and falls to the floor.

Can you think of examples of physical laws or concepts you learned during your youth that have helped you in some way in your career? We'd be interested to hear your stories.

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