Long Answer
Medium difficulty • Structured explanation
Question 1
Long FormDescribe Galileo's contribution to the law of inertia, contrast it with Aristotle's view, and explain how Newton extended Galileo's ideas into his First Law of Motion.
- Aristotle incorrectly held that a continuous external force is necessary to keep a body in motion; in the absence of force, bodies come to rest, which matched common experience but was fundamentally wrong.
- The flaw in Aristotle's view is that he ignored friction—bodies stop because of friction, not because of the absence of a driving force; if friction were absent, uniform motion would persist indefinitely.
- Galileo studied motion on inclined planes and used the double inclined plane experiment to show that a ball always rises to its original height; on a horizontal frictionless surface it would move forever.
- Galileo concluded that rest and uniform linear motion are equivalent states, both characterised by zero net force and zero acceleration; changing this state requires an external force.
- Newton formalised Galileo's insight as his First Law: every body continues in its state of rest or uniform motion in a straight line unless compelled by an external force; this defines both force and inertia.
- Inertia, meaning resistance to change, is the key property: bodies resist changes to their state of motion; the more massive a body, the greater its inertia and the greater the force needed to change its motion.