Variables and the invariables

Out of PCM or physics, chemistry and maths, what I loved during engineering was physics. Even now the love continues. What makes it preferrable to the others would deserve an entire post. And I have worked as a physics lecturer at a JEE coaching institure too. Apart from lectures my work included making new physics questions for the student tests.

Making a good question is an art in itself. When I was preparing for JEE there was this book of physics problems written by a russian called I.E.Irodov . The book was like the final thing one could do, after you had done everyother book around, and your concept was totally clear, you took on Irodov. The questions of Irodov were just different. Let me explain what I mean. The ordinary question in a normal physics book would use a formula, which has n variables. It would give n-1 variable and then ask you to calculate the one variable it had not provided. Or if it was a complicated question it would use 2 or 3 formulas, where each variable that you found would have to be used in the next formula to get another variable. How Irodov differed was that it did not make it obvious which formula a question reffered too. Needless to say Irodov has been a great inspiration for me.

So I’ll put some questions which I have framed and anyone interested can solve them.

Here goes the first:

Q1. It was a silent night, and I was sitting in my balcony. Suddenly I saw a rocket (fireworks) explode in the distance.  After 4 seconds I heard the sound of the explosion. Can you get the distance between you and the explosion?

Q2. I was lying on my bed trying to sleep. I could hear the “tup” “tup” sound of a leaking tap (or faucet) in my bath. After a little while I realized that the duration between each sound was around 12 seconds. Can you get the litres of water getting leaked in a day?

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