How Everything Works Questions and answers about the physics of everyday life http://www.howeverythingworks.org Copyright 2009, Louis Bloomfield en-us lab3e@virginia.edu (Lou Bloomfield) Mon, 06 Sep 2010 18:00:02 EDT Mon, 06 Sep 2010 18:00:02 EDT 60 http://blogs.law.harvard.edu/tech/rss Can DC electric motors reverse directions immediately? Modern brushless DC motors can handle direction reversal amazingly well. They can even generate electricity during those reversals. Mon, 09 Aug 2010 10:04:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1591 http://www.howeverythingworks.org/page1.php?QNum=1591 Does light speed up as it gets further from the sun? In empty space, light always travels at the same speed—the Speed of Light. Tue, 03 Aug 2010 14:54:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1590 http://www.howeverythingworks.org/page1.php?QNum=1590 Why does water change from liquid to gas at temperatures below 212 F? Water can evaporate to form gaseous water (steam) at any temperature, not just at its boiling temperature of 212 F. Mon, 02 Aug 2010 10:53:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1589 http://www.howeverythingworks.org/page1.php?QNum=1589 Why does ice float on water? Ice is less dense than water, so it floats. Fri, 30 Jul 2010 09:09:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1588 http://www.howeverythingworks.org/page1.php?QNum=1588 How big is the electric circuit that powers a lamp in my house? The electric circuit powering a lamp in your house extends only as far as a nearby transformer. Thu, 29 Jul 2010 10:01:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1587 http://www.howeverythingworks.org/page1.php?QNum=1587 What does the f-number of a camera lens mean? The f-number measures the relative brightness of the image cast by the lens. Smaller f-numbers produce brighter images, but with less depth of focus. Wed, 28 Jul 2010 08:03:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1586 http://www.howeverythingworks.org/page1.php?QNum=1586 What happens when you leave a fork in food while microwaving that food? A metal fork might spark in a microwave oven, but once the cooking is done both the fork and food are safe. Tue, 27 Jul 2010 09:27:39 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1585 http://www.howeverythingworks.org/page1.php?QNum=1585 Do you have a solution to the Deepwater Horizon Oil Spill? To stop the oil flow up the 3+ mile well hole, fill that well hole with cannonballs or other dense, hydrodynamically streamlined iron or steel objects. Sun, 30 May 2010 00:00:00 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1584 http://www.howeverythingworks.org/page1.php?QNum=1584 What happens to the wax when a candle burns? A candle's wax doesn't simple transform into a liquid, it also vaporizes into a gas and that gas burns in air to become water vapor and carbon dioxide. Thu, 01 Oct 2009 11:27:31 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1583 http://www.howeverythingworks.org/page1.php?QNum=1583 Why does combining red, green, and blue light create white light? Our eyes sense color by measuring the relative brightnesses of the red, green, and blue portions of the light spectrum. When all three are present, we perceive white. Fri, 17 Apr 2009 07:48:27 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1582 http://www.howeverythingworks.org/page1.php?QNum=1582 Does removing two tubes in a four-tube fluorescent fixture save energy? Most four-tube fluorescent fixtures can operate with only two tubes and will consume only half as much energy. If you don't need the light, remove the tubes. Tue, 07 Apr 2009 14:36:35 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1581 http://www.howeverythingworks.org/page1.php?QNum=1581 How can I describe a polymer to a group of 4th grade students? Polymers are giant molecules formed by sticking together many small molecules. They're properties depend on how they're assembled. Thu, 02 Apr 2009 09:16:36 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1580 http://www.howeverythingworks.org/page1.php?QNum=1580 If a microwave oven door reflects microwaves, why doesn't everything? The door of a microwave oven is specially designed to reflect microwaves, while most objects in our environment are not. Tue, 31 Mar 2009 09:33:03 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1579 http://www.howeverythingworks.org/page1.php?QNum=1579 Do fluorescent lamps really use less energy than incandescent bulbs? Fluorescent lamps are between 4 and 6 times as energy efficient as incandescent lightbulbs and they last many times longer, too. It's time for incandescent bulbs to go. Fri, 27 Mar 2009 10:39:57 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1578 http://www.howeverythingworks.org/page1.php?QNum=1578 Why does adding salt to water make an egg float? A hard-boiled egg weighs almost exactly as much as the water it displaces. By varying the density of that water slightly, you can make the egg float or sink. Thu, 26 Mar 2009 14:40:37 EDT lab3e@virginia.edu (Lou Bloomfield) http://www.howeverythingworks.org/page1.php?QNum=1577 http://www.howeverythingworks.org/page1.php?QNum=1577