journal of science education

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Classroom

In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. "Classroom" is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science.

Head-On Collision of Two Balls Revisited

P H Talapadtur

We present a dramatic demonstration which is also a simple, and an extremely low-cost experiment of head-on collision of two balls in a vertical direction. The advantages of this phenomenon in the vertical direction are clarified. Some simple estimates are made. A thorough analysis of this simple topic is then made, which includes various special and limiting cases, conditions of collision, change of reference frame, etc. .

Address for Correspondence
Umapati Pattar and A W Joshi
Department of Physics
University of Pune
Pune 411 007, India.

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How Far Apart are Primes?
Bertrand’s Postulate

P H Talapadtur

It is well-known that there are arbitrarily large gaps between primes. Indeed, given any natural number $n$, the numbers (n+1)!+2, (n+1)!+3,..., (n+1)!+(n+1) being large multiples of 2,3, ..., n+1 respectively, are all composite numbers.

Let us now ask ourselves the following question. If we start with a natural number n and start going through the numbers n+1,n+2 etc., how far do we have to go before hitting a prime?

Address for Correspondence
B Sury
Indian Statistical Institute
8th Mile Mysore Road
Bangalore 560 059, India.
Email: sury@isibang.ac.in

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