Bob Doyle

Bob Doyle

Each summer, I have an opportunity to teach a sequence of two general physics courses. In the first course, topics are motion, forces, gravity, momentum, rotary motion, statics (balancing of forces), fluids, gases, heat and thermodynamics (how heat moves).

What makes this first course enjoyable is that there are many practical every day applications. There are problems involving cars stopping, cars being driven off a cliff, cannons firing at castles, elevators, skiing, cars making turns on icy roads, why satellites don’t crash, why athletes high jump with their eyes facing the sky, why chimpanzees can be stronger than adult humans, why the Romans used arches (some of which are still standing), how to find if a crown is pure gold, how molecules in a room can break the speed of sound and not hurt when they collide with our faces, how the smell of perfume (and other odors) can travel through a room and how much heat travels through a closed window on a cold day.

Since I have taught these courses for decades, I have seen changes in students. You must come to terms with students who are more skilled in using their expensive smart phones than a $12 calculator. Also there is widespread use of plastic credit cards so both students and adults are less able to estimate how much a series of items costs or to make change.

Every summer, I start each of my physics courses with a review of basic math such as fractions, making conversions (such as from feet to meters), solving basic equations, short cuts with formulae, handling very big and very small numbers and making back of the envelope estimates such as how much bird droppings fall on cars in Cumberland each day).

I also learn from my students. Allegany High School students taught me “Sohcahtoa,” not an Indian name but a way to remember the three basic trig functions — sine, cosine and tangent.

Here is a summary of how I conduct a typical physics class in summer school, which could be adopted for any class in a quantitative subject (such as chemistry, physical geography and economics). I look over the concepts that I will cover in that class. I create three problems that each involves the main concepts to be covered.

In my class on fluids, we dealt with pressure, density and fluid flow. So I made up three problems — one about a submarine, another on the density of a meteorite and the third on the speed of material flushed down a toilet.

Using the relevant equations introduced in that class, I worked each of these three problems on a whiteboard or blackboard, carefully explaining all the steps in handling the equations.

I used my own basic scientific calculator using numbers that were typical of the situations. (I made up the numbers on the spur of the moment.) Once in a while, I would make a mistake and students would correct me.

I welcomed their corrections so they would realize that mistakes happen and everyone needs to be careful and look over their work. All this time, the students were taking careful notes, recording the steps in each problem.

I have the students work in pairs (10 students in total). I then passed out the classwork (prepared in advance) consisting of three pairs of problems. Each student in a pair would work three problems — one submarine problem, one meteorite problem and one toilet flushing problem.

Their numbers were different so they would get different answers. But I encouraged the pairs to check each other’s work before they handed their work in. The student pairs worked together very effectively, noting any confusion that either student might have had with their work.

I collected the classwork and graded them all that day. This classwork was worth 30% of their grade. At the next class I returned their graded work so the students could see how well they did or what mistakes were made.

So every student had feedback on the basic concepts that were covered in that class. I could see if any student was having difficulties from day to day.

For each weekday, I spent about 2.5 hours in class and up to four hours in preparation (class work) and grading (labs, homework and tests).

I welcome any reactions or comments from students or teachers. You are invited to send me an email at . I will respond to any remarks sent to me.

SKY SIGHTS AHEAD: This coming Tuesday, the moon’s motion will carry it from the morning to the evening side of the sun (New Moon). By July 4, you may be able to see a slender crescent low in the western dusk.

This is also the day when the Earth is farthest from the sun for the year at 94.5 million miles. The reason for the seasons is the tilt of the Earth’s axis; in early summer our part of the world is tipped towards the sun, resulting in a high sky path and long daylight hours (close to 15 hours).

Bob Doyle, professor emeritus at Frostburg State University, invites any readers comments and questions. E-mail him at He is available as a speaker on his column topics.

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