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How to Calculate a Bomb's Terminal Speed

Terminal speed or terminal velocity refers to the maximum rate at which a falling object can accelerate. This is dependent upon several factors: the object's weight, the altitude from which it is dropped, its frontal area and the drag coefficient. Since the altitude, and therefore air density, constantly changes throughout the fall, the drag coefficient will also change constantly. It is therefore necessary to use calculus to determine the terminal velocity for a falling object. Fortunately, NASA provides a terminal velocity calculator on its website, so all that is needed are a few simple measurements.

Scales
Tape measure
Altimeter
Drag coefficient table

Instructions

- 1
  
  A very large scale will likely be required in order to weigh a bomb.
  
  Find the weight of the bomb using the scales. The NASA terminal velocity calculator can accept measurements in metric or English units.
- 2
  
  Area can be measured in English or metric units.
  
  Measure the cross-sectional area of the bomb. This is also called the frontal area because it is the area of the bomb that will point down while falling. For square objects, A = L x W. For a streamlined body like a bomb, A = pi / 4D^2, where
  
  A = area; L = length; W = width; D = diameter; pi = 3.1416
- 3
  Find the correct drag coefficient using the manufacturer's specifications or a drag coefficient table. These values are derived experimentally and will change depending on atmospheric conditions.
- 4
  
  At very high altitudes, mountain climbers must use oxygen tanks in order to breathe.
  
  Determine the altitude from which the bomb will be dropped. Since air is less dense at higher altitudes, the density at all altitudes through which the bomb will fall must be taken into account when calculating terminal velocity.
- 5
  Plug the measurements into the NASA terminal velocity calculator and press "Compute."

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