Why is the Newton's first law of motion also called the law of inertia?
According to Newton's first law of motion, every object tends to remain in state of uniform motion or rest unless an external force acts upon it. This shows that a body, by itself, cannot change its state of rest or of uniform motion. This inability of body to change its state of rest or of uniform motion along the straight line is called inertia. Thus, the Newton's first law defines inertia, and hence it is also called the law of inertia.
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