L.R. Ingersoll Physics Museum
UW–⁠Madison Department of Physics

Newton Scale

WHAT TO DO

  1. Step onto the scale.
  2. Read your mass in kilograms!

WHAT IS HAPPENING?

This compression scale has a spring inside that compresses in proportion to how much gravitational force is applied to the scale, unlike the Inertial Balance exhibit, which uses an object’s resistance to motion to demonstrate it’s mass. The relationship between force and mass is given by Newton’s 2nd Law.

Newton’s 2nd Law:

The force, F, on an object is equal to its mass, m, multiplied by its acceleration, a, or F=ma.

For this scale, the force acting on the object is the force due to gravity (the object’s weight). Since the acceleration due gravity is a constant (a=9.81 m/s2 = 32.2 ft/s2), the readout of the scale shows your force divided by the acceleration due to gravity, or your gravitational mass.

Physics Lecture Demonstration Database