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Bullet on board ... To kill or not to kill!

Visualise a loaded pistol flying through space at 10,000 kmph with its butt end facing the direction of motion and barrel pointing backwards.

Published: 04th March 2017 10:00 PM  |   Last Updated: 04th March 2017 08:18 AM   |  A+A-

Visualise a loaded pistol flying through space at 10,000 kmph with its butt end facing the direction of motion and barrel pointing backwards. It now shoots a bullet at 1000 kmph. Obviously, from the pistol’s perspective the bullet will be receding backwards from it at 1000 kmph but to an outside observer it would still be travelling in the direction of the pistol but at 9000 kmph. Correct so far? Good. Now increase the bullet’s speed to 10,000 kmph. This means it’ll barely be able to leave the barrel.

In other words, if you’re right behind and you pull the trigger, you won’t be able to kill yourself. Or what? (Continued in ‘But Google This Now #2’ . . .)


(The prehistoric problem was about a magnetic knight piece on a metal cube that had a 3x3 grid drawn on each face and you had to do some complicated calculation with it if you get my point, etc.)

The maximum number of moves that a chess knight, placed on the centre square of the top face of the cube, could complete, if it lands on no square more than once, is 54. In other words, the knight can touch all the 54 squares before it lands on the square that it began on. There are probably many ways in which the knight can touch all the squares. -- K Narayana Murty, k_n_murty@yahoo.com

(The second problem was: “A, B, C and D have to cross a bridge at night which can hold at most two persons at a time and each crossing must take place with a lit candle which burns for only 17 minutes. A, B, C and D take 1, 2, 5 and 10 minutes respectively to cross. Any two persons must walk at the rate of the slower person.”)

I am afraid this isn’t difficult at all. (But I’m afraid the first problem was too difficult which is why none of you even tried it! – MS) It is clear that C and D should cross together. It is also evident that someone must already be there before C and D attempt to cross. A and B start; A returns; C and D cross; B returns; A and B cross taking 2 + 1 + 10 + 2 + 2 = 17 minutes. -- Saishankar Swaminathan, saishankar482@gmail.com

A and B (1 and 2 minutes) should go first and A should come back with the candle. C and D (5 and 10 minutes) should then go and B should come back with the candle. Now, A and B should go to the other side with the candle. So, total time will be 2 + 1 + 10 + 2 + 2 = 17 minutes. -- Rekha G, g.rekhapai@gmail.com

(The third one was: “What emotion is an anagram of a homonym of an antonym of a homonym of an anagram of WOLF?”)

A WOLF eats a FOWL whether it is in a FOUL or FAIR mood. The fowl becomes an easy FARE and naturally it is in constant FEAR (not only of the wolf but also of MS and his Endgames!). – Dr Ramakrishna Easwaran, drrke12@gmail.com

An anagram of WOLF is FOWL. The homonym of FOWL is FOUL. The Antonym of FOUL is FAIR. The homonym of FAIR is FARE. The anagram of FARE is FEAR. That’s it! The emotion is FEAR. -- Ramakrishna Bhogadi, rambhogadi@gmail.com

(Among the first five who also got it correct are: Dr Vinayak Shukla, shukla58@hotmail.com; Raghunath K, rakhunath.k@gmail.com; Rajesh R, rajesh56rr@gmail.com; R Viswanathan, rviswanathan2001@yahoo.com; Neethi Balagopal, neethibala@gmail.com.)

1. Take an empty steel drum. Go to the beach, invert it and try to push it into the water. When released it bobs up. The more you push it down, the greater force it seems to come out with. Is it possible in the ocean that when pushed down far enough it just floats or sinks? If so what happens to the energy (the work done pushing it down)?
2. (Continued from first para . . .) But now what if that pistol was in orbit around Earth when it shot the bullet backwards at 1000 kmph? Like a rocket firing its engines, the pistol would gain in velocity. This would put it in a higher orbit. Which means it would start slowing down to conserve angular momentum. On the other hand the bullet would get into a lower orbit and thus increase its speed. Someone watching from Earth should then notice the bullet first catching up with the pistol and later actually overtaking it. Or what?

Sharma is a scriptwriter and former editor of Science Today magazine.

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