Ramsay Mechanical Practice Test

The Law of Inertia, formulated by Sir Isaac Newton, states that an object at rest will remain at rest unless acted upon by an external force. This principle underlines the concept that objects naturally resist changes to their state of motion. In practical terms, if there is no net force applied to an object that’s not moving, it will not start moving on its own; instead, it will remain stationary.

In this context, the choice stating that an object will remain at rest unless acted upon is consistent with everyday observations. For example, a book lying on a table will not move unless someone pushes it. This is a direct application of the Law of Inertia.

The other choices reflect misunderstandings of this principle: an object in motion doesn’t automatically apply to objects at rest without external force; suggesting that an object begins moving without an external force contradicts the Law itself; and the idea that an object's speed increases gradually implies some form of continuous force acting upon it, which also goes against the requirement of an external force in the Law of Inertia. Hence, the accurate choice aligns precisely with the fundamental premise of inertia as defined in classical physics.