Not just motion ....
https://www.zmescience.com/other/map-of-countries-officially-not-using-the-metric-system/
Explain the value or importance of International system of units when describing motion
2 answers
The most obvious item is weight and mass
In English units we tend to sort of confusingly express mass in pounds, which is a unit of force, but only useful on earth.
Therefore to calculate the acceleration we need to somehow use weight / g.
for mass sometimes we use pounds/32 = weight force in pounds/g = slugs
Then you can get pounds force to accelerate along a line= m a where m is in slugs and a is in ft/s^2
However that is all pretty awkward compared to using mass in kilograms and distance in meters. F in Newtons = mass in kilograms * acceleration in m/s^2
if you want weight force on earth then it is simply m g where m is kilograms and g is about 9.81 m/s^2 on earth
The nautical mile is an exception. It is useful because it represents a minute of arc ( one degree/60 ) around a great circle on earth. This is easier to use for navigation with a sextant than meters.
In English units we tend to sort of confusingly express mass in pounds, which is a unit of force, but only useful on earth.
Therefore to calculate the acceleration we need to somehow use weight / g.
for mass sometimes we use pounds/32 = weight force in pounds/g = slugs
Then you can get pounds force to accelerate along a line= m a where m is in slugs and a is in ft/s^2
However that is all pretty awkward compared to using mass in kilograms and distance in meters. F in Newtons = mass in kilograms * acceleration in m/s^2
if you want weight force on earth then it is simply m g where m is kilograms and g is about 9.81 m/s^2 on earth
The nautical mile is an exception. It is useful because it represents a minute of arc ( one degree/60 ) around a great circle on earth. This is easier to use for navigation with a sextant than meters.