Gravitational and inertial mass

Gravitational and inertial mass

We can measure the mass of an object by comparing its weight to the weight of a known object, using a balance. If the known object has a weight of 9.8 Newton,  its mass is 1 kg. If the test object also has a weight of 9.8 N, we say its mass is also 1 kg.

We measure the inertial mass of an object by having a force changing the movement of the object when that movement is in a horizontal plane in order to prevent gravity to change the readings. A simple inertial balance is like this: (


The object is placed on a support attached to two metal strips. These strips can move horizontally only when a force pushes it aside from rest position. The movement back and fro depends on the amount of mass on the support: big mass will cause a slow back and fro movement; small mass will cause a fast back and fro movement. If the frequency of different tested mass is plotted on a chart, an unknown mass is used and from the chart its inertial mass can be calculated.

The question asked for years was this: is there a difference between inertial mass and gravitational mass.

With the advent of apparatus that can increase the weight of an object or decreased its weight using an horizontal laminar light beam, a new verification is now possible.

Take two 100 g  mass. Each has a weight of 0.98N.

Put one 100 g mass over the apparatus and one under the apparatus. When 100 g mass under the light starts to levitate, put it on an inertial balance. Put the 100 g mass that was over the apparatus with  an increased weight on another inertial balance.

Give each balance a small push horizontally and note the frequency of each one. The frequency will be very close to one another even if one has almost triple the weight of the other one.

Put a third mass of 0.98 N on one of the inertial balance and compare the frequency. The frequency of the light mass is almost double.

That will show that the weight of the object is simply a force on the object and does not change the mass of the object.

Conclusion: If 2 objects have the same weight and are both subjected to the same gravity, they will also have the same inertial mass.

We hope that many laboratories will start to make the apparatus to change the weight of objects. In 2016, there was only one of these on planet earth.

About Louis

In this site, I will give a summary of the discoveries to date and the new one also. My family helps me a lot: Benoît is discussing the findings; my wife Madeleine, a nurse is helping also. My daughter Rosanne devised this WEB site and her husband Jamie is a proficient programmer who can help me a lot, even with his big family of 7 nice kids. I am now retired after 52 years of teaching mostly physics and maths. Bonjour Je suis un professeur de sciences depuis plus de 50 ans. J’ai enseigné de la 7e année à la 12e puis à l’université d’Ottawa et enfin au collèege. J’enseigne depuis plus de 25 ans au collège Boréal, Sudbury, Ontario, Canada. Depuis le début, je désirais comprendre la gravité. Après beaucoup d’essai infructueux, j’ai découvert qu’un rayon de lumière peut bloquer la force de gravité. Encore beaucoup de recherche permettront de comprendre la nature de la gravité. Mon grand gars Benoît ia fait un baccalauréat en Sciences infirmières . Il m’a beaucoup encouragé dans ma recherche. Mon épouse Madeleine est infirmière et ma grande fille Rosanne a réussi à faire ce site WEB malgré le travail avec ses 7 beaux enfants. Mon gendre Jamie Parent est programmeur et très habile avec les ordinateurs. Louis Joseph Rancourt
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