People are often confused about the difference between weight (mass) and force. Weighing machines measure weight (mass) in pounds (lb) or kgs (kg), etc. Force gauges, on the other hand, measure force in Newtons. (In the us, other units such as lbf, ozf and kgf are also being used. ) One Newton is understood to be the force needed to accelerate 1 kilogram of mass at the rate of 1 meter per second every second. You can feel this one Newton force by putting a small apple (100 g) on your side.
The apple’s weight (mass) is constant anywhere in the universe. When dropped, it falls freely to the Earth. In outer space, instead of falling it floats, even though its weight (mass) is unrevised. What causes the apple to fall or drift? The force caused by the object’s weight (mass*) and gravity velocity, or as derived from Newton’s Second Law of Motion: force = mass times velocity.
On earth the apple falls at a continually increasing rate of speed called gravity velocity. Gravity velocity varies dependant on latitude, level and other factors. Gravity velocity at 45 degrees latitude, sea level is 9. 80665 m/S2. In 1901, the Conference on Weights and Measures set 9. 80665 m/S2 as the standard International Gravity Velocity value. gravityAcceleration
To be the cause of the deviation in gravity velocity at different latitudes and elevations, weighing machines need to be calibrated at and used at their location. A small apple assessed on a scale calibrated in Paris, france does not measure the apple’s correct weight in New york.
Force gauges, once calibrated for local Force Gauge acceleration*, will measure the correct force values anywhere in the universe. A 100-lb weight (mass) may produce more or less force than 100 lbf due to the deviation in local gravity velocity. A 100-lb weight (mass*) produces 100 lbf force only at the International Gravity Velocity value of 9. 80665 m/S2.
The formula for local force (lbf) produced by a 100-lb weight (mass*) is calculated as below: