Concept that gravity is caused by the matter

The educational resource shows a visual about the difference between mass and weight: mass is not the same as weight, although in ordinary life both words are used with the same meaning.

Concept of indirect measurements

The educational resource shows a visual about the free fall in vacuum: whatever their shape and mass, all bodies fall with the same speed in a vacuum.

The educational resource shows a visual about the free fall in air: when a body falls through a fluid such as air, its shape is important.

Concept of attraction among masses