Horsepower / Power in Watts Required to Overcome Air Resistance

IMPERIAL

The horsepower required to overcome air resistance is the speed in miles per hour, cubed, times the frontal area in square feet divided by 150,000

Where:

MPH = Speed in miles per hour

FA = Frontal area in square feet

HP = Horsepower

150,000 = A conversion constant

Example:

What is the horsepower required to overcome air resistance of a vehicle travelling 40 miles per hour and having a frontal area of 80 square feet?

METRIC

The power in watts required to overcome air resistance is the speed in kilometres per hour, cubed, times the frontal area in square metres divided by 77.86

Where:

MPH = Speed in kilometres per hour

FA = Frontal area in square metres

P = Power in Watts

77.86 = A conversion constant

Example:

What is the power in watts required to overcome air resistance of a vehicle travelling 65 kilometres per hour and having a frontal area of 7.5 m2?