# How the moon rocks ...... and all that jazz!

Guys you didn’t hear me. When I said that I’d withhold your email ID if you wanted me to I also said that in that case please make sure you let us know where your corporeal body currently resides.

Published: 16th September 2017 10:00 PM  |   Last Updated: 16th September 2017 07:58 PM   |  A+A-

Guys you didn’t hear me. When I said that I’d withhold your email ID if you wanted me to I also said that in that case please make sure you let us know where your corporeal body currently resides. We don’t want an address; just a city, town or whatever will do. Without that info I’m sorry I can’t run your response. Life’s tough, no?

If not, then an astronaut has a spring balance and a 1.0 kg rock A, which when hung on the balance on Earth gives a reading of 9.8 newtons. Arriving on the moon at a place where the acceleration of gravity has a value of about 1/6 the acceleration of gravity at the Earth’s surface, he picks a rock B which gives a reading of 9.8 newtons when weighed on the spring balance. He then hangs A and B over two sides of a pulley and sees that B falls with an acceleration of 1.2 m s^–2 . What is the mass of stone B?

THROUGHPUT

(The problem was about finding the minimum drops required with which to determine the floor from which it’s safe to drop pomegranates. And of course all the usual guff.)
The minimum number of drops required are eight. We begin from floor #8. If it does not break, we continue in the following fashion: 8, (8 + 7), (8 + 7 + 6), (8 + 7 + 6 + 5), (8 + 7 + 6 + 5 + 4), (8 + 7 + 6 + 5 + 4 + 3), (8 + 7 + 6 + 5 + 4 + 3 + 2), (8 + 7 + 6 + 5 + 4 + 3 + 2 + 1) = 8, 15, 21, 26, 30, 33, 35, 36. Suppose the pomegranate breaks from 20th floor, It will not break from the eighth; it will not break from the fifteenth; it will break from the twenty first. You still have one pomegranate left. Now start dropping from the 16th floor moving up one floor every time. It will not break till 19th and it will break from 20th floor. -- Dhruv Narayan, dhruv510@gmail.com
(The second one was: “Manidoowaaling island is the largest freshwater lake island in the world. It also holds another world record.”)

This island is now called Manitoulin Island and is a Canadian lake island in Lake Huron. It’s other world record is it contains a number of lakes of its own. In order of size, its three most prominent lakes are Lake Manitou, Lake Kagawong and Lake Mindemoya. Each of these in turn has islands within them, the largest of them being Lake Mindemoya’s 82-acre Treasure Island, located in the centre of Manitoulin. -- Shashi Shekher Thakur, shashishekher@yahoo.com

Each of these three lakes have islands within them, the largest of these being Lake Mindemoya’s 82 acre Treasure Island, located in the centre of Manitoulin. This is the largest island in a fresh water lake in an island in a fresh water lake in the world. -- Venkateswaran R, venkateswaranjanaki@gmail.com
(The third problem was: “If it’s 6.45 pm right now, what’s the time going to be 23,999,997 hours later?”)

The time will be 3:45 pm. 23,999,997 hours will be just three hours less than 1,000,000  days (24*1,000,000 minus three hours). Deducting three hours from 6:45 pm gives the answer. I actually did not note the time taken for the solution, but I am sure it was less than 10 seconds. -- Dr P Gnanaseharan, gnanam.chithrabanu@gmail.com

Dividing 23,999,997 by 24, we get 21 as the remainder add this to 6.45 pm, we get 3.45 pm as the answer. Took me 30 seconds like you said. -- Aniruddha Rao, aniruddharao741@gmail.com
It is now 3.45 pm as 23,999,997 is just short of 24000000 by three hours only a million days hence. Best of luck to those who started with 23999997 divided by 24. -- Ramakrishna Easwaran, drrke12@gmail.com

(Among the first five who also got it right are: Vijayalakshmi Sudheer, vijisudheer62@gmail.com; Ramesh Kumar, rameshkumarthayyil@gmail.com; Saishankar Swaminathan, saishankar482@gmail.com; Vasisht Vasudevan, (ID withheld on request); Lipika Muthu, geelipm@gmail.com; A V Ramana Rao, raoavr@gmail.com . . . Continued in BGTN.)

1. Interesting variation: today is a Monday; what day will it be after 23,999,997 hours, with all those complications of leap years and so on? – (Submitted by Prof S Manikutty, manikuti@iima.ac.in)
2. A greenhouse which is usually made of glass is designed to keep plants in a warm environment. How? (No, not just through the global “greenhouse effect”.)

Sharma is a scriptwriter and former editor of Science Today magazine.(mukul.mindsport@gmail.com)

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moon jazz