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HP 30S Using the Built-in Physical Constants
Example 2: Find the quotient between the proton mass and the electron mass.
Solution:
This ratio is one of the built-in constants on the HP48GX and the HP49G+ and is called “mpme.” Although
it’s not in the above list, you can calculate its value by pressing:
š<<<<</š@@@@@@yy
Answer:
mP/me = 1836.152663. Compare it with the value on the HP 48GX (1836.152701) and the one calculated
on the HP 33S (1836.1526633). Greater accuracy in measures implies new standard values. Constants are
not that constant after all!
Example 3: Einstein observed that any change in mass implies a change in energy and vice versa. Calculate the
energy change corresponding to a change in mass of 1Kg.
Solution:
Einstein’s most famous equation states that:
2
c
m
E
⋅
∆
=
∆
c is the speed of the light in the free space, and we can use the value built in our calculator. Since the
change of mass is 1 in this example, the problem is reduced to squaring c. Press:
šqy
Answer: 8.987551787·10
16
J
Example 4: A cylindrical tank contains 4 kg of carbon monoxide at –50ºC (223K). The tank is 1 meter in length and its
inner diameter is 0.2 m. Calculate the pressure of the gas using Van de Waals’ equation.
Solution:
This equation explains derivations from ideal gas behavior and is:
RT
)
b
V
)(
V
a
P
(
=
−
+
2
where a and b are constants characteristics of a particular gas; for the carbon monoxide they are 0.1474
and 3.95·10
–5
respectively. Solving for P:
2
V
a
b
V
RT
P
−
−
=
Before starting to calculate, notice that V is actually the molar volume and, when expressed in m
3
, is equal
to:
2
2
0
4000
7
.
V
⋅
π
=
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HP 30S Using the Built-in Physical Constants - Version 1.0
