The tendency of a body to retain in its position of rest is known as the inertia of rest. It was Galileo who first asserted that objects move with constant speed when no external forces act on them. The inherent property of a material body by virtue of which it cannot change, by itself, its state of rest or of uniform motion in a straight line is known as inertia. Internal forces within an object can’t cause a change in the overall motion of that object.
However, the force of gravity that the inner core of the moon exerts on the outer crust of the moon is an example of internal force on the moon. For instance, the force of gravity that exerts on the moon is the external force on the moon. The external force is the force acting from outside on an object rather than the force from inside of an object. Newton’s first law of motion is also coming to be considered as the law of inertia. In other words, an object at rest remains at rest, or if in motion, remains in motion at a constant velocity that tends to retain its inertia until and unless acted on by a net external force. There are three of Newton’s Laws of Motion Newton’s First Law of motionĪccording to Newton’s First law of motion, Everybody continues in its state of rest or of uniform motion in a straight line unless it is compelled by some external force to change that state. 1.4.1 Example of Newton’s Third Law of Motion Explain Newton’s Laws of MotionĪt one time, matter was known to be anything that occupies space and has mass but with the upcoming understanding of Newton’s laws of motion developed a new fact about matter defined it to be anything that occupies space and has its own mass and inertia.