内容正文:
外刊阅读 ▶ “答案与解析”见P3
重而圆的石块在水面上弹跳得更高
Have
you
ever
spent
a
long
time
searching
the
beach
for
flat(扁平的)
stones
to
skim(掠
过)
across
the
sea?
Wel,
you
might
have
been
wasting
your
time
because
a
new
study
has
found
that
heavy
and
rounded
stones
wil
make
bigger
leaps
out
of
the
water.
When
you
throw
a
thin,
flat
stone
across
the
water,
you
wil
often
see
it
skim
along
the
surface
several
times.
With
a
rounded
stone,
the
effect
is
different.
It
might
only
jump
once,
but,
if
thrown
right,
it
wil
bounce(弹 跳)
much
higher,
according
to
researchers.
Doctor
Ryan
Palmer
and
Professor
Frank
Smith
used
maths
to
work
out
how
the
shape
and
weight
of
an
object
affect
how
it
hits
the
water.
They
discovered
that
although
some
heavy
stones
wil
sink,
stones
which
have
a
special
kind
of
curve(曲面)
wil
bounce.
This
is
because
the
curve
changes
how
the
stone
interacts(相互作用)
with
the
water.
A
stone
that
is
rounded
and
heavy
presses
into
the
water
more
deeply
and
longer.
This
pressure
is
what
causes
the
water
to
make
the
stone
upwards,
▲ .
Palmer
said
rounded
rocks
are
a
game-
changer.
“If
youve
got
a
heavier
rock,
you
can
get
a
superelastic(超弹性的)
response.
You
get
a
single
big
bounce
rather
than
lots
of
little
bounces.
Its
very
satisfying
if
you
can
achieve
it,”
he
said.
Palmer
and
Smiths
research
is
al
about
how
objects
interact
with
surfaces,
so
it
wont
just
be
used
to
help
people
skim
stones.
The
main
aim
of
the
research
was
to
study
how
ice
builds
up
on
a
plane
when
it
is
flying,