Schijnbaar gewicht

Consider an elevator at rest, having a box on a weighing scale. The gravitational force on the box equals the normal force exerted by the scale on the box, such that the magnitude of the net force on the box is zero. The scale reads the magnitude of the normal force, which is the true weight of the box.

If the elevator moves upward with a constant acceleration, the net magnitude of the force on the box equals the difference between the normal force and the gravitational force on it. The scale reads the apparent weight higher than the true weight of the box.

When the elevator accelerates downward, conventionally, the acceleration becomes negative. The apparent weight is now lower than the true weight of the box.

Now, if the elevator's cable breaks, the box with the scale will momentarily hover but eventually accelerate downward due to gravity, experiencing a free fall.

The scale reads zero, and the box appears weightless. This phenomenon is termed apparent weightlessness.