Pressure, Density, Mass, Crushing Strength,
Area Volume Tension, and Wing Loading
Steve Belovarich
Eduardo Garcia
Adam Morgenstern
Craig Etienne
Pressure
 Pressure
is the force per
unit area
 Or, weight divided by area
P = W / A
 Pressure = Weight / Area
 A cubic
foot of steel
weights about 500 lbs
 The bottom face of this
cube has an area of 1
square foot
 So, the pressure exerted
on this bottom face is :
= 500 lbs/square foot
Density
 Density
is the weight per
unit volume
 Or, weight divided by
volume
D = W / V
 Density = Weight / Volume
 A steel
cube has a weight
of 500 lbs
 The cube is 1 cubic foot
 So, the density is :
= 500 lbs per cubic foot
Mass
 Mass
is the aspect of matter
that is affected by forces,
according to physical laws.
 We perceive the mass of an
object when we try to move it

When we try to lift an
object, we perceive its
mass as weight, due to
the gravitational force that
the earth exerts on it.
 Your
mass is how much
you weigh
 The mass of the steel
cube is 500 lbs.
 The mass of a 10 lb
weight is 10 lbs!!
Crushing Strength

The ability to withstand
pressure exerted on the
object by gravity and the
object’s mass.
 Example:
Could there be a
King Kong?
 NO!
 A King Kong would weigh
8000 times as much at it’s
bones could support
 It’s own weight would
crush its bones into
splinters!!!
Area Volume Tension
 Area-Volume Tension is a
result of the fact that when an
object is scaled up, the
volume of this object
increases faster than the
surface area and faster than
areas of cross sections.
 The reason for this is that as
an object is scaled up, it’s
volume goes up with the cube
of the linear scaling factor,
whereas the surface area of
the object only goes up with
the square of the linear
scaling factor.
 A α L2 and V α L3 (or L α
V1/3)
so…A α V2/3
Area Volume Tension
 A cat can jump out a 2 story
window and be unharmed,
whereas a human would probably
break a few bones. If we think of
a human of a scaled up version of
a cat, this makes sense. The
kinetic energy gained by a falling
object is proportional to its
weight, and therefore is
proportional to it’s volume. On
impact, most of this energy is
absorbed over the surface area of
the object. Since volume scales
faster than area, the energy gained
scales faster than the surface area
to absorb the energy. Therefore,
the human has more potential for
injury.
Wing Loading
 The
weight being
supported divided by the
area of the wings
 Usually measured in
pounds / square feet
 Proportional to the power
necessary for sustained
flight
 Proportional
to the length
of the flying object
when scaling up or down,
weight changes with the
cube of the length of the
object. Wing area changes
with the square of the
length.
Wing Loading continued…
 Ex: to scale up a plane by a factor of 5:
it weighs 53 or 125 times as much
but only has 52 or 25 times as much wing area
Therefore, each square foot of wing must
support 5 times as much weight.
The End