Once a week, All-School Assembly launches with the Teacher On Active Duty (TOAD) sharing something of interest—a reflection, a story or song, a demonstration of some sort, or a simple poem. In this way, the community gets to know one of our own a little better. The TOAD this week, Owen Coyle, shared a list of ten ways to use physics when camping and hiking. Mr. Coyle teaches science, math, and computer science; is an advisor to freshman boys; and coaches the JV boys’ cross country team. His TOADTalk is featured below.
I hope you all had a lovely and restorative Winter Camping and Wellness Weekend. This weekend I had the pleasure of accompanying a small band of Thacher ninth graders on a classic Thacher backpacking adventure, spending Friday night at Patton's Cabin before hiking up and over Nordhoff Ridge and arriving back on campus in time for dinner on Saturday. We had gorgeous weather, light packs, and an all-around great time, though at least my legs are having some regrets in hindsight.
I had planned something else for this TOADTalk, but halfway through our trip, I had an epiphany that made me switch topics. You see, for those of you who don't know, one of the many hats I wear here is teaching ninth grade physics. I love teaching physics, but one of the things that can be challenging is the difficulty and perceived lack of usefulness of the subject. When the going gets tough, it is not uncommon for many students to ask themselves, and perhaps even their teachers, "Why do we have to know this?" After all, most of you are not going to grow up to be physicists. The Bureau of Labor Statistics determined that of the estimated 131 million Americans working full-time, only about 18,000 are employed as "physicists." For perspective, that's roughly one out of 8,000 workers. Things get a little better when you look at college degrees. In 2017, the last year for which I could find data, 8,813 undergraduates majored in physics, out of a total pool of approximately two million bachelor's degrees. That works out to 1 physics major for every 227 college graduates. So, statistically speaking, one of you out there might major in physics! Am I helping my case here?
And yet, though it might be perceived to be a niche subject, physics is all around us, all the time, even more than the other sciences, at least in my opinion. I mean, when was the last time you had to use chemistry in your everyday life? (Well, except for cooking and cleaning, of course!) And maybe it has to do with the fact that I am who I am, and I teach what I teach, and I was leading a trip exclusively of ninth-grade students, all of whom were currently taking physics, but physics kept coming up on our trip, without me even trying to bring it up. More than that, not only did physics keep coming up, but we found ourselves using our understanding of physics to be better campers and hikers.
So without further ado, here are Ten Ways that Physics Knowledge is Useful While Camping and Hiking, presented in roughly chronological order of when they came up (and these were only the best examples, I had to edit this list down for time).
1. Become a Master at the Ring Swinging Game
As I mentioned earlier, we spent our first night at Patton's Cabin, and while waiting for dinner to finish cooking, Javi decided to play a few rounds of that game where you swing the ring on a string and try to land it on a hook on the other side of the room. Javi being the good physics student that he is, quickly realized that the best strategy was to release the ring at a height just above the nail on the other side of the room. The reason this is a winning strategy is because as the ring swings down, potential energy is converted to kinetic energy before being converted back to potential energy as the ring swings back upwards. If you start the ring from a height only just above the nail, the ring will have just enough energy to make it to the nail, without having excess kinetic energy that would cause it to overshoot. Using this strategy, Javi was able to make around 50 percent of the shots he took.
2. Always Make Sure You Have At Least 1 Newton of Snickers Bars Per Person
In physics, the distinction between mass (how much stuff is in an object) and weight (the force of gravity on that stuff) is important, and because weight is a force, we don't measure it in kilograms or pounds, but newtons (N), which is not a unit that most of us are familiar with. As any good physics student will tell you, though, the weight of an object is equal to the object's mass (measured in kilograms) times the acceleration due to gravity (which is about 10 m/s2). Because Snickers bars have a mass of about 50 g, 1 N is approximately equal to the weight of 2 Snickers bars. For reasons completely unrelated to physics, our Snickers ration was 2 Snickers bars per person, which the boys were quick to point out meant we each had 1 N (they also made sure I snapped a photo to commemorate this for their physics teacher Doc Q).
3. Measuring the Depth of an Outhouse
Patton's Cabin isn't the Ritz Carlton, but as far as camping accommodations go, it is pretty fancy. Undoubtedly, one of its best features is having a dedicated outhouse. One of the peculiarities of using an outhouse though, is the delay between "the release" and "the thud". Now I don't remember who first noticed this, but we quickly realized we could use this information to measure the depth of the hole, using nothing but our ears, and d=12gt2(the equation for the distance an object falls in freefall). Using this method, we estimated the depth of the outhouse hole to be between 4 and 8 ft, which is pretty hand-wavy, but it's my fault because I told the boys they couldn't bring stopwatches with them to the toilet.
4. Newton's Law of Cooling and Camp Stoves
This next one involves something we don't teach in physics but instead in math class here at Thacher, which is Newton's Law of Cooling, which says that the temperature of an object decays exponentially with time. Another way of saying this is that the rate at which an object loses heat is proportional to the difference between that object's temperature and the outside temperature, so the hotter an object gets, the faster it loses heat to the outside air. This matters if, like me, you are trying to boil a pot of river water using a very empty fuel can that is not putting out much heat, on a very cold morning in the Sespe. While things can look good for a while, as the water in the pot gets hotter, it also loses heat faster, and depending on how cold the morning is and how low on fuel you are, the pot may wind up losing heat as quickly as your stove can add it, never coming to a boil. Luckily, Patton's Cabin has a small stove hooked up to a propane tank and protected from the wind, so we were still able to have our beloved oatmeal and hot chocolate without risk of giardia.
5. Estimating and Checking Your Travel Times
After our hearty breakfast, we set off with full stomachs for the 14-mile hike back to campus. We had used trail-time calculators to estimate the total hiking time, but of course you want to check your progress along the way, and estimate how long it will take to hit the next checkpoint. We found ourselves constantly doing this using our map, and d=r t (the distance covered = avg. speed multiplied by time). For instance, we knew that it was about 5 miles from Patton's Cabin to our first major checkpoint: the fork between East Fork and West Fork Lion camps. Using a typical walking speed of 2 mph, we calculated that it should take us about 2.5 hours to get there, so when it took us only 2 hours, we knew we were making good time.
6. Using or Not Using the Mechanical Advantage of Trails
While we made good time from Patton's Cabin to our first checkpoint, unfortunately we made a wrong turn and wound up at West Fork Lion Camp. We were thus faced with a choice: hike back 1/4 mile to the spot where we missed the turn, or hike straight up the 200 feet of steep hillside it would take to reach the trail. This being a group of ninth grade boys, it was an easy choice, hike straight up. Now from a physics perspective, this has a certain kind of logic, it should take the same amount of work to hike straight up the hill as it does to hike back and then hike up the trail (your change in potential energy is the same regardless). However, a trail can be thought of as a ramp, one of the basic simple machines like a pulley or a lever, all of which let you trade force for distance. So while you are doing the same amount of work walking straight up the hill versus going back and then hiking up the trail, because the trail spreads that work over a much longer distance, it reduces the amount of force you have to exert over that distance, making the job much more manageable. Nevertheless, we persisted, determined not to give up our hard won mileage...until halfway up the slope got so steep that we could not walk straight up anymore. I was at least able to convince them to walk diagonally up the hill in the direction where the trail would slope down to meet us, rather than continually rising higher and higher above us. So, use or don't use the mechanical advantage offered to you by trails, the choice is yours.
7. Conserving Energy on the Trail … Using Conservation of Energy
Needless to say, once we made it back to the trail, we were pretty tired, and we had only climbed 200 feet of the 2000 feet of total elevation gain needed to make it to the top of Nordhoff Ridge. As we continued to climb, and the time since breakfast continued to wear on, we soon realized we would need to find a way to be as efficient with our energy output as we could. One way we found to do this was using the Law of Conservation of Energy. Imagine a skateboarder in a half pipe. When the skateboarder is at the top of the halfpipe, they have a lot of potential energy. As they ride down the halfpipe, this potential energy is converted to kinetic energy, causing the skateboarder to speed up. On the other side of the pipe, as the skateboarder rises, their kinetic energy is converted back into potential energy, bringing them to the top again. The way that we used this on the trail, was when we encountered a small dip in the trail, rather than fighting the slope on the downslope, we would just allow our legs to speed up, using the kinetic energy we gained to carry us up the other side, using less energy than if we had fought the downslope and then had to climb back up again. Obviously this technique only works for small dips and good terrain where you can stay in control though, so use it carefully.
8. Using Chemical Potential Energy for a Final Boost
As we neared the top of the trail, we knew we would need one final boost of energy to make the pinnacle. It was time to reach for some chemical potential energy—snack time! But how much energy would we need to make it to the top? Thankfully, our ninth-graders had earlier in the year calculated how much chemical potential energy was in a Snickers bar, a whopping 900,000 J, which is incidentally enough to bring a compact car up to a speed of about 90 mph if you could convert it with 100 percent efficiency. People are unfortunately not 100 percent efficient, more like 25%, but even still, it was enough to replenish our reserves and push us over the top. Incidentally, I actually did the math, and for a 130 lb hiker carrying 30 lbs of gear assuming 25 percent efficiency, it takes almost exactly two Snickers bars to climb the 2000 ft from Lion Camp to Nordhoff Ridge. So always bring at least two Snickers bars with you; they only weigh 1 N, but they pack a punch energy-wise!
9. Do We Have Time For a Snowball Fight?
As we neared the peak on our Snickers-powered second wind, we saw what looked like snow on the north face of Nordhoff Ridge. Having both run varsity cross country in the fall, Nico and Javi wanted to know if we had time to run over to the snow and have a snowball fight. Checking the map, we estimated that it was about 1 mile to the snow along the dirt ridge road. We had 30 minutes to spare, which we calculated was enough time, despite the elevation and less than ideal footwear, and so we decided to go for it. 30 minutes and one cowboy hat full of snow later, we settled down to a hearty lunch of PB and J bagels, followed by Nutella "dessert bagels." On the way down the mountain, having tacked on an extra 2 miles to what was already a 14-mile day, Javi admitted that finally, for the first time at Thacher, we had succeeded in wearing him out.
10. How to Bring Snow Back to Campus...
Finally, let's say that hypothetically, you are a ninth-grade boy, and have heard the tales that, if there is snow at Assembly, the School will get a holiday. How would you bring said snow back, over hours of hiking, and another day and a half of waiting? Well in a vacuum-insulated water bottle of course! [With that, Mr. Coyle’s camping companions produced a container of actual snow that, impressive as it was, unfortunately did not convince Ms. Pidduck to grant a School holiday.]