# THIS ( NEWTONIAN) LIFE

## BARRIE FRASER

IT starts in primary school. I hate having to learn multiplication tables. I fail mental arithmetic, this sort of thing: if Johnny is six years older than Mary, and the sum of their ages is 20, and I am two years older than Mary, how old am I?

Some smart little kid would immediately answer: nine. How did he do that? I’m failing mathematics, right?

But wait. Fast forward to age 12. I learn about elementary algebraic equations: let Mary’s age be x, then Johnny’s age is x + 6; after a couple of lines of equation bookkeeping, all is transparent. I love it.

Move on to second- year high school, we are studying mechanics. Newton’s laws of motion: a particle occupies a point in space and has a mass. Law 1: a particle will continue in a state of rest or of uniform motion in a straight line until it is acted upon by an impressed force, the text informs me.

I ponder this statement. I know about force: bigger boys bullying me in the playground. I was OK with the notion of a particle with mass. I imagine tennis and cricket balls. But how could a particle possibly travel with uniform motion in a straight line? I understand about the velocity of a particle and how to calculate it, so this must mean the velocity of the particle is constant or zero. No object in my limited experience travels in a straight line near the earth’s surface. All the tennis and cricket balls I have experienced are acted on by the force of gravity, or someone throwing them or hitting them with a bat.

Curious, I think it’s very hard to imagine one of these Newtonian particles travelling in a straight line. I ponder and ponder. Suddenly I understand. Suddenly I can do Newton’s thought experiment and imagine a single lonely particle moving in free infinite space with no force acting on it.

With understanding comes a tremendous admiration for Newton. The genius who had been able to imagine the motion of this lonely particle in infinite empty space. A thing that doesn’t exist in the physical world. The law is a pure abstraction, the result of an experiment that can only be carried out in the mind. But, coupled with his second law, that the resultant force on a particle is equal to its mass multiplied by its acceleration, it explains so much. All the problems in the mechanics text, certainly.

I start working out the problems at the end of the chapter ( answers in parenthesis at the end of each question). To my delight I keep getting the correct answers.

Imagine my intoxication, and my disappointment, when my mates do not share my enthusiasm for the joy of Newton’s laws. That laws of nature could be expressed concisely in mathematical formulae is wonderful to me.

Then, in my final year of high school, we learn calculus. Here’s the problem that gets me hooked: Johnny ( he’s always the naughty one) pours ink on his desktop at a steady rate of x cubic inches per second. The ink spreads on the table in a circular pool of uniform depth, h. Find a formula for the radius of the pool as a function of the time. Calculus solves this and many other problems. The power of Newtonian mechanics explodes and I am hooked for life.

My obsession at the age of 70 is a theory for wrinkling sheets of steel. There is no cure, but I do get paid for it.

thislife@ theaustralian. com. au