391 miles per hour in feet per second

Conversion

391 miles per hour is equivalent to 573.466666666667 feet per second.^[1]

Conversion in the opposite direction

The inverse of the conversion factor is that 1 foot per second is equal to 0.00174378051615903 times 391 miles per hour.

It can also be expressed as: 391 miles per hour is equal to $\frac{1}{0.00174378051615903}$ feet per second.

Approximation

An approximate numerical result would be: three hundred and ninety-one miles per hour is about five hundred and seventy-three point four seven feet per second, or alternatively, a foot per second is about zero times three hundred and ninety-one miles per hour.

Units involved

This is how the units in this conversion are defined:

Miles Per Hour

"Miles per hour (abbreviated mph, MPH or mi/h) is an imperial and United States customary unit of speed expressing the number of statute miles covered in one hour. Although kilometres per hour is now the most widely used measure of speed, miles per hour remains the standard unit for speed limits in the United States, the United Kingdom, Antigua & Barbuda and Puerto Rico, although the latter two use kilometres for long distances."

Wikipedia page of miles per hour

Feet Per Second

'The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s, or sec). The corresponding unit in the International System of Units (SI) is the metre per second.Abbreviations include ft/s, ft/sec and fps, and the rarely used scientific notation ft s−1.'

Wikipedia page of feet per second

Footnotes

[1] The precision is 15 significant digits (fourteen digits to the right of the decimal point).

Results may contain small errors due to the use of floating point arithmetic.