B R Sitaram
Here are the answers to last month’s questions!
How come we do not have four seasons (summer, autumn, winter and spring) in the tropics? Which months would be the hottest near the equator?
In the region between the tropic of Cancer and the tropic of Capricorn, the sun is overhead at noon twice a year. (On the two tropics, it is overhead at noon only once a year.) As a result, two times in a year, the heat from the sun will be maximum! For example, at the equator, the sun is overhead on both the equinoxes. On both the solstices, the angle made by the sun is the same (23.5 degrees). As a result, in the absence of other geographical factors, one can expect two seasons that are relatively cool and two that are relatively hot. Very close to the equator, the hottest months are those that immediately follow the equinoxes and occur twice a year.
2. If someone tells you that a particular product is not made of chemicals, what would your response be?
Unfortunately, the image that is conjured up by the word “chemical” is that of bottles of acids and bases kept in a lab. If by a chemical we mean something that is studied in chemistry, then that includes every atom and molecule in the universe! Oxygen is a chemical, as is water (if you are not convinced, try putting a piece of sodium metal in water!). In this sense, saying that something is not made of chemicals is equivalent to saying that it does not exist! What is meant, of course, is that this particular product has no harmful constituents!
3. Vehicle tyres, as you would have seen, have lots of treads. Obviously, treads increase friction. But you do not need fancy treads to do this, all you need is a rough surface. Why do tyres have such treads then?
Actually, the treads are designed to take care of a more dangerous phenomenon – aquaplaning. When you are travelling over a pool of water, a thin film forms between the tyre and the road. This film greatly reduces the friction between the vehicle and the road and increases the chances of skidding. The treads are designed to throw this water to the side, to minimize the chances of formation of the film. You may have noticed while driving in the rain that water fountains out of the sides of the tyres!
4. The other day, I was using an elevator when I caught sight of a notice, “Maximum 8 passengers, 544 kg”. Why this strange number, 544? Why not 550, 500 or 600 kg?
This is the result of taking a perfectly sensible number in one system of units (the FPS or Imperial system) and converting it mindlessly to another (the MKS or SI). In this example, 544 kg works out to 1199.31 pounds or 149.91375 pounds per person. What someone has done is to start with 150 pounds per person (a very reasonable number!), multiplied it by 8 to get 1200 pounds, converted this to kilos (544.3108 kg) and then rounded this off to 544 kg. It would have been more sensible to use a round figure like 550 kg!
Questions for this month
- Our textbooks say that the spring equinox is on March 21. However, this year, the spring equinox falls on March 20 (at 9:20 am). How come there is this difference?
- Which law or laws of physics are violated or can be violated by living organisms?
- Why did the British government announce an award for a method to measure the longitude of a ship, while no such award was announced or made for determining the latitude of a ship? (The longitude award was announced in 1714 but was never awarded; however, many persons got financial assistance in carrying out research to solve the problem.)
- Your friend’s daughter has just been to the moon on an exchange visit for a few months and has sent you a painting of the lunar sky with the sun at the centre. What is the most important novel feature that you will notice as soon as you look at this picture?
Send in your answers and comments to [email protected].