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Joe Wechsler asked, Does sugar dissolve faster/better in warm than cold water water?

The straightforward answer to the question is: Yes. Sugar dissolves faster (though not better)

What’s more interesting, however, is the reason for this.

To understand it, we first need to understand what we mean by dissolving. Lets take a look at sugar. A sugar cube, or sugar-powder is made up of millions and millions of molecules of sucrose.

These are held together in a crystalline form, making a lattice. Because so many molecules are collected together, we can SEE the powder or the cube. Now, say we put the sugar in a glass of water. Inside the glass, the water molecules are moving around rapidly, because of the heat energy they possess. As the sugar comes in, these molecules start bumping into the sugar, knocking the molecules here and there. Slowly, all the molecules of sugar get separated from each other and because each individual molecule is too small for us to see, it disappears.

Now, what is the difference between hot and cold water?

At the molecular level, a difference in the temperature is a difference in the ENERGY of the molecules. In hot water, the molecules are moving around more vigorously than in cold water. They tend to separate out the sugar molecules even more quickly.

And hence, sugar dissolves rapidly in warm water.

Tags: cold, dissolves, sugar, warm, water

A.V. Rahul Swamy asked, How does the lights in the traffic signal automatically change? Does it have brains?

So let us say you have light pole 1 which has just turned green. 

At the same time, the light pole 2 has turned red. 

Now both these lights are running on similar timer circuits which are running parallel. 

So, light pole 1 will turn first orange after 55 seconds, and red after 5 more. By that time, light pole 2 must turn green. So their cycles run like the following:

Light Pole 1: G - O - R -O - G - O - R -O - G - O - R -O - G - O - R -O - G - O - R -O - G - O - R -O - G - O - R 

Light Pole 2: G -O - R - O - G -O - R - O - G -O - R - O - G -O - R - O - G -O - R - O - G -O - R - O - G 

The gap between Light pole 1 and 2, is called the ‘phase difference’. In this case, it is a difference of 60 seconds. Both the timers are exactly the same, but one is started 60 seconds after the first. As long as the circuit keeps working, the system will work fine. 

So, from the outside, it will look like traffic lights have brains. But, it is just a clever circuit made by an engineer that makes it work!

Today’s traffic lights are more complex. They have circuits that don’t rely solely on timing, but also synchronize different traffic junctions. So, even if one timer fails, the signal from another timer will make it work correctly. Lights can also be controlled from a central station when the traffic situation changes. In some countries, you have traffic lights that detect if there is any traffic waiting at a red-light and will decided to turn green based on that! So technology is moving very fast! You can read more by looking at http://en.wikipedia.org/wiki/Traffic_light

Tags: cycles technology, pattern, signals, timer, traffic

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Prasanna Kumari asked, how can i introduce trigonometry through an experiment?

A simple experiment which students of even class 8 could do is to construct a home made clinometer and using it to find the height of a tall tree or building near the school.

The clinometer can be made by taping a drinking straw to the hypotenuse of the isosceles set square present in a students’ geometry box and attaching a makeshift plumbline to it. You can visit the link below for more details on making and using it.

http://www.4j.lane.edu/partners/eweb/ttr/mckenzie/resources/ideabank/use%20a%20simple%20clinometer

You could plan it as a group activity and each group could later be asked to reason out the logic behind the method. You can also have the class explore side ratios of right angled triangles to discover that the ratios for given angles remain the same irrespective of side lengths. These would lay the foundation for a discussion on the scope and history of Trigonometry.

Later the students can also be challenged to find whether the other set square could be used for the experiment and if so, how should it be held and what adjustments would need to be made to the computations.

Tags: challenge, Maths, squares, Trigonometery