Sunday, July 1, 2012

Physics in IRL

Originally a facebook status update of mine.


My first try at applying classroom physics to a practical situation.

I was sitting on my desk(at home), taking a break from calculating the time that a ball thrown by some guy takes to reach maximum height and the range that it would cover horizontally. I looked outside the window at the drizzle. I spotted water drops falling from a pipe on the terrace onto the ground. "Lo behold!" I thought, "Let's calculate the height of my house." Using the pen as a bookmark, I closed the book. Pushed it aside with the textbook and gathered my watch, a pen and a book in which I planned to jot down the readings. I remembered doing a similar problem at college.

Taking my stop-watch, I measured the time difference between two successive rain drops falling onto the ground. After a few observations, I found it to be 0.6 seconds. I kept my watch aside and tried to insert the formula's into one of the kinematic equations. I got the answer something along the lines of 3m. It didn't feel right. I wondered as to what went wrong or why I was getting inconsistent values. I assumed it was some observation error so I took the measurements again. As I said, I wanted to do it a bit differently to see if I'd get the same answer. This time, I looked up and calculated the time that one drop took to reach the ground from the pipe. I measured it and the reading said "1.00" and I was like, "This cannot be happening. I got a 0.6 previously. Why am I getting such a big difference?" I measured again and this time, I got a "1.03s" and the next time, I got a "1.05s". While I didn't understand the discrepancy then, later, I realized that in the first case, in trying to reduce my work by measuring something simpler, I had instead measured something else. Instead of measuring the time that a drop takes to fall to the ground from the pipe, I had accidentally measured the time interval between two drops in being released by the pipe."

Now that I got my values, I substituted them and found out that the height of my house was 4.93m and I was like "That cannot be true. This building looks so tall, how can it be just 5m." but the scientific Adarsh inside me said "Physic's can't be wrong." I replied "But if I take wrong values, it can be misleading." S.A. replied "Did you?" I managed a "uh....I don't think so. No." Then the answer's simple, "your house is 4.93 m tall or 16.17 feet tall approx."

## Come to think of it, I could have managed to make this calculation more efficient by taking the average time that drops take to fall onto the ground from the pipe. I had instead calculated it drop by drop and then taken the average.

Anyway, that was actually fun.

......Another idea just hit me...Be right back..Oh wait, it's night already?


I soon got a comment telling me that the drop would attain terminal velocity and that I'd need to modify my equation a bit to get to the right answer. Well, maybe I'll get back to this one day once I get an idea of what terminal velocity is.

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