"change in" occurs so often in physics that we replace it with the Greek letter delta, whose upper and lower case forms are Δ and δ. We'll write x for displacement and t for time. That fraction above looks long and clumsy when written in words. His average speed is written, pronounced 'v bar'. We signify the average of something by putting a bar over it. Let's see how special: What if he travelled at 2 m/s for half a second, stopped for one second, then travelled at 2 m/s for another half second? He would still have travelled two metres in two seconds, so his average speed would be 1 m/s, even if he were never travelling at this speed. Now this is a special case, because in this example he is travelling at constant speed. So what is v? Displacement has increased by 2 m, time has increased by 2 s, so v is When the clock reads t = 2 s, he is at x = 5 m. We call this his initial displacement and write x 0 = 3 m. When the clock strikes zero, he is at x = 3 m. By the way, the magnitude of velocity is called the speed, which we could write as | v|. In these examples, we shall consider only motion in a straight line, so we can specify the direction simply thus: Positive velocity means going to the right, negative velocity means going to the left. So here we could say that his speed is 1 m/s but his velocity is 1 m/s towards the right. ( An aside for physicists: velocity is a vector, meaning that it has direction as well as magnitude. This means that, for each second he travels, his displacement from the starting position increases by 1 m. The strange man in this animation is moving in a straight line at a constant speed of one metre per second. The velocity is the rate of change of displacement. This page supports the Physclips project.ĭifferentiation: How rapidly does something change? What is a logarithm? A brief introductionĭifferential Equations: some simple examples (separate page).Integration: How do the results of a variable rate add up?.Differentiation: How rapidly does something change?.This short introduction is no substitute, however, for a good high school calculus course: we shall take some short cuts of which mathematicians may disapprove. So stick with us: differentiation really is just subtracting and dividing, and integration really is just multiplying and adding. Fortunately, one can do a lot of introductory physics with just a few of the basic techniques. For physics, you'll need at least some of the simplest and most important concepts from calculus. Calculus analyses things that change, and physics is much concerned with changes. The basic ideas are not more difficult than that. The flow is the time derivative of the water in the bucket. Here's a simple example: the bucket at right integrates the flow from the tap over time. Calculus: differentials, integrals and partial derivatives.Ĭalculus – differentiation, integration etc.
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