Physics can be difficult to learn, but this blog aims to help you get into physics by connecting your GCSE physics lessons with things you see in the world around you.

## Tuesday, 7 February 2012

### Precision Counts

Watching the TV the other night, I was confounded by an advert that promised “the search for fast”. And I thought, shouldn’t that be “the search for speed”? Now, I know that arguing with the TV is pointless, and definitely always ends up with you looking a bit mental and nothing resolved, but this one really stuck in my brain.

What is fast exactly? As a scientist, it’s a loose term you can use to describe how someone or something moves, eg that car is moving fast. But it doesn’t really tell you anything, since it’s relative. If the car were overtaken by a train, you might say that the car is still fast but the train is faster. But that’s not really the whole of the story.

When it comes to science, it’s not just numbers that you need to worry about – words are important too. They can tell you a lot about the problem that you’re trying to solve so pay attention! I’ve spoken several times about the difference between speed and velocity, with speed being a directionless way of measuring how fast something is going, whilst velocity is also about direction.

What that means in practical terms is that if you imagine a car going around a race track at a steady speed of 50 mph, the velocity will be changing as the track twists and turns. This can be a confusing concept to start with, but once you get to grips with this and other important distinctions in the language of science, you’ll start to see things in a new light.

Start by thinking about what the difference is between weight and mass for example (hint, one of them changes with gravity and one doesn’t) or between force and weight.

Ok, so becoming a bit picky and precise about words might lead you to rant about an advert and its search for “fast”. What is that? And how do you search for it?? But at least you’ll be thinking critically about what words to use to accurately describe things, and that will make me glad.