## Archive for the ‘Kinematics’ category

### Physics is a *moving* science

July 21, 2013

Don’t start crying – it’s not about emotion, its all about motion. On second thoughts, you might want to cry after all – this unit we start pulling out the maths, and we just WON’T STOP! There is a lot to get done, and less time to do it in, but we’ve already talked about how much harder you are going to have to work this semester, so I won’t go into that any further.

The important thing to remember, when we are solving equations or drawing graphs is that PHYSICS IS NOT A MATHEMATICAL SUBJECT! Mathematics may be one of the techniques we use to model, analyse or predict what will happen in a situation, but the important thing is the concepts and theories underneath – you must understand the ideas below the mathematics. This is why the major task I have assigned to you so far is all about your “reading record”, not a list of questions. Keep in mind you must try and understand the “why” before you start analysing the “how” with the formulas.

This is not to say that you can ignore the mathematical components -NO! But it is equally important that you make sure that you understand both parts of the science – the Mathematical (data, formulas, graphs and equations) and the Conceptual (Theories, Laws and explanations).

### Gravity Sucks!

April 5, 2013

There is an unbearable pun about gravity. The fact that it is both a pun, and unbearable explains both why I know it, and why I would choose to inflict it on you. Of course, I won’t just say it, but imply that it exists – relying on the fact that right now, every bad pun about gravity is rolling through your head, and if not your fingers are twitching to Google whatever it is I am talking about – thus my purpose is achieved with minimal effort!

Regardless, the orbital movement is the final context of motion in two dimensions, our first area of study. It is clearly an outgrowth of circular motion, but it has some interesting twists of its own. For a start, the force that maintains the circular trajectory is the force of gravity – the first of the four forces of the standard model of physics. Gravity has some difference from other forces that you have thus far encountered. As an example, both Weight force (F = mg) and Elastic force (F = -kx) only involve the object that the force is affecting. Newton’s universal law of gravitation has some similarities to the weight force, but a great many more differences.

### Twistin’ and Turnin’ – Circular motion will set your brain a-burnin!

February 16, 2013

So. You’re back – you survived one year of physics, and you decided to come back for another. If you’re smart, you’re a bit scared! If you’re smarter, you’re already working your backside off and planning how you can work harder. This year we are starting with a review of 1-D kinematics from last year, and quickly moving into 2-D applications of the same ideas. The first one we are spending time on is circular motion – that is objects moving in a circle in either the vertical or horizontal plane.

Circular motion is hard to get your head around in the beginning, because your own experience is lying to you. Everyone has ridden in a car as it goes around a corner in the road or a roundabout – and you have felt the force “pushing you towards the outside of the curve”, so when you think about these forces, you have an immediate expectation that the force is acting outwards – from the centre of the circle out…

But you would be wrong!