We suppose that a person maintains with the hands a pen and billiard ball of bird. She wishes to find out what of these objects will fall to the ground first if the release from the same height and at the same time. First, the person must develop a hypothesis… “It seems that the ball will fall to the ground before the pen if loose both at the same time and from the same height.”

Experiment and Data collection

The in charge person will drop the billiard ball and the pen a certain number of times from the same height and another one must collect the data when writing down in a notebook what of the objects falls first to the ground every time. After to have dropped the objects some 5 times the person must add the number of times that each object has arrived at the ground first, is made something thus:

Analysis of the Data and Conclusions

Finally, after to have demonstrated that the billiard ball arrived at the ground first in 5 occasions, the person could conluir that his hipótesisi seems correct. The ball IF it arrives first at the ground! This way, the data are collected to verify a hypothesis and the analysis of the data is used to prove or to reject a theory.

NOTE: We make you notice that in fact one has reached the incorrect conclusion.

During many years one thought that the propose idea by the Greek philosopher Aristotle, who maintained that the heavy bodies fall faster than the slight bodies were a total truth. Almost two centuries later, the Italian scientist Galileo Galilei questioned this aristotelian idea and affirmed that the bodies, as much the light ones as the heavy ones, fall with the same rapidity. One says that, in 1591, Galileo, being professor of the University of Pisa, he congregated a group of teachers so that they were witnesses of an important experiment. Galileo, with the help of a pair of assistants, raised the stop of the Tower of Pisa to drop simultaneously two great spheres, one of wood and another one of lead. The spheres arrived at the same time at the floor. If Aristotle had been right, the lead sphere would have arrived long before at the floor. The conclusion to that Galileo arrived is that in the absence of air, when not existing sustenation some (friction with the air), the flattened bodies, as the pen or a sheet of paper with their expensive parallel to the floor, fall as fast as a ball. In 1642, the Irish scientist Robert Boyle confirmed this result when dropping a bullet of lead and a pen within a glass container to which the air was extracted to him. With this experiment, Boyle demonstrated that the only force that reduces the speed of the bodies in its fall is the air resistance. In 1971, the mission Apolo XV arrived at the Moon, that lacks atmosphere. Astronaut David Scott dropped from the same height and at the same time a hammer and a pen; after wonder of the thousands of viewers who were present at this Earth experiment, both objects reached the lunar ground at the same time, and so the astronaut exclaimed: “They see, Galileo was right”