HP 32S and HP 32SII Week: Total Drag
Introduction
The following equation calculates the total drag force applied to parallel to an area in the opposite direction of the object's motion.
Fd = 1/2 * ρ * v^2 * Cd * A, ρ = P / (R * T)
ρ = air pressure
P = absolute pressure (101,325 Pa, 14.696 psi, 2116.224 lb/ft^2)
R = specific gas constant (287.03 J/(kg k), 53.3533 (ft lbf/lb °R))
T = temperature (K = °C + 273.15, °R = °F + 459.67)
A = cross area that the drag force is applied (m^2, ft^2)
V = velocity of the object (m/s, ft/s)
Cd = drag coefficient (unitless)
The program gives outputs:
ρ = air pressure (kg/m^3, lb/ft^3)
Fd = total drag (kg*m/s^2, lb*ft/s^2)
HP 32S/32SII Program: Total Drag, SI Units
Size: 55.5 bytes
F01 LBL F
F02 INPUT C
F03 INPUT A
F04 INPUT V
F05 INPUT T
F06 273.15
F07 +
F08 287.03
F09 ×
F10 1/x
F11 101,325
F12 ×
F13 STOP
F14 RCL× C
F15 RCL× A
F16 RCL V
F17 x^2
F18 ×
F19 2
F20 ÷
F21 STOP
Example:
C = drag coefficient = 0.31
A = area =7.0686 m^2
T = temperature = 18.8 °C
V = velocity = 3 m/s
Results:
ρ = 1.20915184207 kg/m^3
Fd = 11.9230799416 kg*m/s^2
HP 32S/32SII Program: Total Drag, US Units
Size: 55.5 bytes
F01 LBL F
F02 INPUT C
F03 INPUT A
F04 INPUT V
F05 INPUT T
F06 459.67
F07 +
F08 53.3533
F09 ×
F10 1/x
F11 2116.224
F12 ×
F13 STOP
F14 RCL× C
F15 RCL× A
F16 RCL V
F17 x^2
F18 ×
F19 2
F20 ÷
F21 STOP
Example:
C = drag coefficient = 0.31
A = area =76.0868 ft^2
T = temperature = 65.84 °F
V = velocity = 9.84252 ft/s
Results:
ρ = 7.54778228E-2 lb/ft^3
Fd = 86.232900381 lb*ft/s^2
Source:
Lindeburg, Michael R. PE Civil Engineering Reference Manual for the PE Exam 14th Edition Professional Publications, Inc: Belmont, CA. pp. 17-41 and 17-42
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