I went to the bike shop to buy a pump. They had several pumps with a gauge with a psi dial and a bar dial. I stuck my thumb on the end and pumped with the other hand and got two bars. Then I figured that if the piston area is 10 cm², I can get just over eight bars by sitting on the handle. So I asked the salesman what the area is. He didn't know. I searched the pump and found that the diameter is 31 mm. "32² is 1024, 31² is 961, so it's seven and a half", I calculated aloud. (I work with computers, so 1024 is a lot more familiar than 961.) That meant I could get almost the full eleven bars by sitting on it. I tried to explain, "I weigh 83, so I multiply by 9.8 to get newtons. A pascal is a newton per square meter. Ten square centimeters is 1/1000 square meter, so that's just over 800 kilopascals. 100 kPa is a bar, so that's just over eight bars." The guy looked at me as if I were telling him baseball scores. "We measure in pounds," he answered. I asked him, "Haven't you heard millibars - or hectopascals - or kilopascals - on the weather report?" He didn't know what I was talking about.
The dimensions on the pump are all metric: Bore:31mm Stroke:540mm (actually that's the length of the tube, the stroke is 513) Volume:410cc³ (sic) The dimensions of tires are metric. The tires have their pressure indicated in bars or kilopascals or both. How does he expect to do his job if he doesn't know metric? phma
