Law of inertia was put forward by Galileo. He conducted various experiments and finally explained the law of inertia. Let us discuss Galileo’s experiments.
Motion of Object on Inclined Plane
Galileo allowed to move the object down the inclined plane. He observed that during motion the object accelerates. In another case, he allowed to move the object up on the inclined plane by applying force . During this experiment he found that the object decelerates. In the third case, he allowed the motion of object on friction less horizontal plane. Galileo found that the object neither experiences accelerate nor retardation and moves with constant speed.
Motion of object on Double Inclined Plane
Now Galileo took a double inclined plane having smooth surface. Originally the ball was at rest. He released the ball from one end so as to begin its motion. The ball moves over the plane and reaches the other end. It was observed that the ball travels nearly the same height on second plane to that of the height at which it is released from first plane. If there is negligible friction then the initial height is equals to final height.
If the slope of second plane is decreased and the experiment is repeated then it was found that the ball reaches nearly the same height, however in this case the ball travels longer distance. Again if the slope is reduced further, same result will be obtained but the ball travel even longer distance.
Finally if the slope is reduced to zero i.e. plane is made horizontal then the ball will ideally travel infinite distance. Or we can say that the ball will never stop its motion . This is the ideal case however in practice forces such as frictional force , air resistance oppose the motion of the ball. Hence the ball travel finite distance and then stops.
Output of Experiments
With these experiments he found that when a body is at rest there is no net force acting on it. Considering ideal scenario, if the body is in uniform motion then there is no need of external force to maintain its uniform motion . Thus the state of rest and the state of uniform motion are equivalent.
It means that even if the body is in rest or in uniform motion the net force acting on it is zero. This is the law of inertia. Law if inertia states that “A body at rest will remain at rest and a body in motion will remain in motion unless and until an external force acts on it”. Inertia means ‘resistance to change’. Thus the body does not change its state of rest or uniform motion unless external force acts on it.
This article is helpful for Class 11 Physics
Keywords: Law of inertia, Force, Frictional force, Galileo experiment
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