Physics Homework: Buoyancy and Archimedes Principle, Assignments of Physics

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Phys
 Due
April
27
in
Class
 
 1






One
cubicmeter
of
air
weighs
1.39
kg.
If
you
heat
it
by
170
C
the
density
reduces
to
.91
 kg/m3
(remember
air
expands
when
you
heat
it).
How
big
do
you
have
to
make
a
hot
air
balloon
 to
carry
a
gondola
of
50
kg,
attached
to
the
skin
of
880
lb
and
you
with
3
friends,
(pick
your
own
 weights
)
 Answer:

One
cubic
meter
hot
air
has
a
buoyancy
of
1.39
‐
.91
=
.48
kg.
To
carry
(50
+
880
∙
2
∙
 .44
+
60
+
80
+
75)
kg,
you
need
1004
∙
.48
=
500
m3.
That
corresponds
to
a
circular
balloon
of
 10
m
diameter

 2








A
tall
glass
(20cm)
is
swimming
in
your
bathtub.
It
weighs
60
grams
and
a
bottom
area
of
 10
cm2.
How
deep
will
it
sink
into
the
water,
while
it
is
still
empty
and
how
much
water
can
you
 add
to
drown
it?
 Answer:
 
 The
glass
will
 sink
 so
 far
until
 the
displaced
water
 is
60gr.
This
 correspond
 to
6
 cm
 since


10cm2
∙
6
cm
=
60cm3
=
60gr
of
water.
Now
14
cm
of
glass
floats
above
the
surface
of
 the
water.

Again
14
cm2
∙
10
cm
=
140
cm3
suffice
to
sink
the
glass.
This
means
you
can
add
 only
140
ml
of
water.