Elementary Physics


Advanced Theoretical Physics, under Creative Commons from Marvin (PA)s photostream, click pic for link.

Advanced Theoretical Physics, under Creative Commons from Marvin (PA)'s photostream, click pic for link.

They had a theoretical physicist on the news this morning, a jovial chap. I like the idea of science that has no grounding in real life at all, grappling with the intricacies of string theory. Still though, some people (coughpedestrianscough) need some sort of basis in elementary physics.


OK: an object is at standstill – it needs a force to get it going. Once it’s going, inertia comes into play to keep the object moving, then an opposite force has to be applied to make that object stop. Friction and gravity come under this banner, just like they do with making the object move in the first place, as well as other, external forces.

OK: applied physics. I’m on a bike, at a junction, stopped. To get me going, I need some sort of external force – at a flat junction, that’s almost solely down to my thigh muscles. I’m a big chap, on a heavy bike, and I’m not all that fit, so the acceleration isn’t all that – I like to push off from lights as quick as possible to get into a rythm quickly.

Once I’m going then, gravity is a good friend of mine when I’m going down a hill, but less so when going up – my bulk causes this, but at 6’3″, there’s not much I can do about that. So I rely on inertia to keep me going so that my thigh muscles can get some degree of respite.

OK, still easy. What this boils down to is that when I am cycling uphill it is ideal for me to keep going, and not to stop. When I slow down or halt, I have to put that much more energy back into getting going again. That’s why I sometimes go through a red light on a pedestrian crossing if no-one’s there, and why sometimes I swerve around (a long way around) someone crossing the road at a zebra crossing. I’m in full control of my bike, it’s just that if I slow down it’s hard to get going again, and 5 miles into a 7 mile ride, I need to be conserving my energy.

I understand that this is against the highway code and the letter of the law, so I’m not particularly proud of it, but it’s totally within the spirit of the law, i.e. to provide safe passage through rights of way for all users of the road. It’s the job of all traffic and pedestrians to be vigilant and aware of what’s going on, and if you are, you have no problem. What it doesn’t give anyone at all the right to do is swear at me vehemently as I circle widely around you, thanks very much.


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