Force and Laws of Motion Class 9 Science - Newton's First Law of Motion.
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Galileo Galilei performed some experiments on object in motion. Newton studied the observation of Galileos Experiment and presented Three Law of Motion. In this video, we will discuss about Galileos experiment and discovery of First Law of Motion.

The following topics are covered in this video -
1) Galileos Experiments -
The frictional force of surface oppose motion of ball, and allows it to stop after a while. Friction can be reduced upto an extent, if surface is smooth, or surface is covered with smooth substance, like oil.
By studying the Galileos observation newton presented Three Laws of Motion.
2) The First Law of Motion -
The first law of motion states that - Body maintain its state of rest or uniform motion allowing straight line, until and unless an unbalanced force acts on it. This property of an object to keep itself in State of Rest or in Uniform Motion is called as Inertia. Hence, First Law of Motion is also Known as Law of Inertia.
3) Inertia and Mass -
Larger the size of object, higher will be tendency to maintain the position of rest. Hence, larger will be the inertia. For example : Inertia of train will be comparatively larger smaller than that of bicycle.

4) Examples based on first law of motion.
Body remain in state of rest in the bus. When driver applies brake, the motion of bus slows down and body maintains its state of rest due to inertia.
While taking a sharp turn, body gets thrown to opposite side. This is because body tries to maintains its motion in straight line.