This is a Clilstore unit. You can link all words to dictionaries.

The experiment of Galileo

 All objects when dropped
from a height fall towards the Earth;
this happens due to the gravitational
force exerted by the earth on the object.
Suppose you drop simultaneously a small
stone and a cotton ball of the same size
from height; which of the two will reach
the ground first? We see that the stone
reaches the ground earlier than the
cotton ball so we may falsely conclude
that the heavier objects fall faster
than the lighter ones, that is, the
acceleration producing heavier objects
is more than in lighter objects.

Galileo showed that all bodies whether light or
heavy fall at the same speed towards the

However, in normal conditions it seems that Galileo was wrong and, as you can see in the video, lighter objects fall slower tan weight objects. We are going to discover why. You will work in groups of four students.


One of you drop a book and a sheet of paper. Observe if one of the objects falls faster.

Why does it happen. Discuss it with your mates.


May be you have decided that the falling speed depends on the weight. I propose you another experiment. Take two sheets, they have the same weight, but  crush one of them until you make a small paper ball with it and drop the normal sheet and the crushed sheet at the same time. The crushed sheet drops faster, but the weight is the same

How is it possible? Discuss it with you partners


Get a sheet and a book that has the same size. Put the sheet on the book and let them drop. They have different weight but drop at the same speed.

How is it possible. Discuss it with your parners.


I am sure that with this experiments you have discovered which invisible think that sorround us makes that lighter objects fall slower although the action of gravity is the same on all falling objects.



If you have find it out, you will be able to answer this question. What happens if an astronaut drops at the same time a hammer and a falcon feather (remember: the moon doesn't have atmophere). This was a real experiment.First discuss it with your group and then look at this video for the answer. The audio is very bad so don't worry if you don't understand it, but look at the feather and the hammer.

Clic on the video if want to watch it full screen in youtube.


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