New Scientist - 19.10.2019

52 | New Scientist | 19 October 2019

The back pages Puzzles

Quick crossword #43 Set by Richard Smyth Quick quiz #25 Puzzle set by Paulo Ferro

#26 Evening out

The figure above is composed of

15 matchsticks. Move 2 matchsticks

to get a 3-digit number with all the

digits even numbers. Find them all!

Answer next week

#25 Car crash maths

Solution

A blue car travelling at 70mph and a yellow

one at 100mph brake simultaneously when

they see a fallen tree ahead. The blue one

stops just in time. But the yellow one hits

the tree at about 70mph, so option (d) is the

best answer. The yellow car hasn’t even got

down to the speed that the blue car was

travelling at. Here is one way to calculate this:

• The energy expended on braking is the
  force × the distance.


• In this model, therefore, both cars expend
  the same amount of energy.


• The blue car braked to a halt and has
  zero energy left.


• Energy in motion (kinetic energy) is
  proportional to ½×mass×velocity², so think
  of both cars losing ½×m×70² of energy.
  •The yellow car started with ½×m×100².


• 70² is not quite half of 100², so the yellow
  car still has half of its energy, which means
  it is still travelling at a touch over 70mph
  when it hits the fallen tree.
  The same result can be reached if you
  use the equations of constant acceleration.
  Our intuition is confused by the squaring
  of the velocities – this isn’t a linear
  relationship. This helps to explain why our
  guesses are often poor in such situations.
  What’s more, this model assumes no
  driver reaction time and some simplification
  of braking forces. In fact, if reaction time is
  included, the yellow car will be travelling
  even faster when it hits the tree.

1 Which 19th century

Scottish physicist’s name is

associated with the unifying

equations of classical

electromagnetism?

2 Pluto, Makemake and

Haumea are the largest

objects in what disc of

icy rocks engirdling the

solar system?

3 What are the individual

tiny tentacled animals that

make up a coral called?

4 What is ITER being built to

demonstrate at Cadarache

in the south of France?

5 What letter must you add

to C 2 H 5 OH to make CH 3 OH?

Answers below

Cryptic

Crossword #16

Answers

ACROSS 7 Angler, 8 Weevil,

9  Beta, 10 Cambrian,

11 Erratic,  13 Essay, 15 Fence,

17  Mineral, 20 Cleavage,

21  Tray,  23 Encode, 24 Garnet

DOWN 1 Ante, 2 Alpaca,

3  Breccia, 4 Swamp, 5 Beards,

6  Himalaya, 12 Riesling,

14  Diverge, 16 Craton,

18  Entire, 19 Facet, 22 Apex

Quick quiz #25

Answers

James Clerk Maxwell 1

The Kuiper belt 2

Polyps 3

Nuclear fusion: it is the 4

International Thermonuclear

Experimental Reactor

M – they are the 5

chemical formulae for

ethanol and methanol

ACROSS

1 Biologist and president

of Humanists UK (5,7)

10 South Korean

social network (7)

11 Turn to vinegar (7)

12 Dolphin genus; bacterium

(informally) (5)

13 Heavy-lift helicopter (8)

15 Irregular heartbeat (10)

16 Mineral, Mg 3 Si 4 O 10 (OH) 2 (4)

18 Palm tree, Euterpe

oleracea (4)

20 Tropical cyclone that

struck Japan in 1990 (7,3)

22 Aromatic herb (8)

24 Consonantal alphabet (5)

26 Tidal wave (7)

27 Ettore ___, automobile

designer (7)

28 Pr (12)

Answers and the next cryptic crossword next week.

DOWN

2 1st or 2nd, say? (3,4)

3 ___ group, COOH (8)

4 ctrl+Y or cmd-shift-Z (4)

5 UV-A lamp (5,5)

6 ___ Ocean, prehistoric

sea between Gondwana

and Laurussia (5)

7 Shrub genus (7)

8 Icicle or brinicle (3,10)

9 Unfounded health

concerns exacerbated

by online research (13)

14 Peridot (10)

17 Red-flowering

eucalyptus (5,3)

19 Inflating tool; the

constellation Antlia (3,4)

21 IT firm founded in

Kawasaki in 1935 (7)

23 Old World lizard (5)

25 Latin abbreviation,

found in endnotes (4)

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