pressure

Not only is this a beautiful demonstration of how much thrust can be generated by a fire hose, it also gives us a glimpse into what firemen might be doing while waiting around at the station when no one's looking. It's also a beautiful demonstration of the principles of rocket propulsion, Newton's third law, and the law of conservation of momentum.

First, let's calculate the approximate thrust generated by each fire hose. Because the hoses are able to accelerate the compact car off of the ground, the combined maximum thrust of the ten hoses must be somewhat greater than the weight of the car. Assuming that the car is on the lighter side -- say 2,000 pounds or so -- then each hose produces a thrust of at least 200 pounds. No wonder firemen have to brace themselves solidly in place when operating one of these babies.

We are proud to introduce today the first installment of our newest regular feature,Kitchen Alchemy. In it, H. Alexander Talbot and Aki Kamozawa, a husband-and-wife cooking duo and authors of the constantly fascinating Ideas in Food blog, will take us through the myriad intersections of food and science; and as an added bonus, each column will also feature an innovative and, needless to say, delicious recipe for putting said science into action. Enjoy. —Eds.

Pressure cookers are among our favorite culinary gadgets. We like them for things as simple as perfectly steamed beets and as playful as caramelized yogurt. And the days of screeching, squealing pressure cookers, shuddering on your range top and conjuring fears of explosions, are on the wane. Today we have quiet, efficient appliances that are used in both professional and home kitchens. Now you can buy electric pressure cookers, which shorten cooking times, are easy to clean and make a minimal amount of noise.