Inertia of Rest: Explaining the Physics Principle

The question asks to identify the property of a body at rest that causes it to remain at rest unless an external force is applied. This fundamental concept is described by inertia.

Inertia is the resistance of any physical object to any change in its state of motion; this includes changes to its speed, direction, or state of rest. When an object is at rest, its inertia is the tendency to stay at rest. This property is a direct consequence of Newton's First Law of Motion, often called the Law of Inertia.

Analyzing the Options:

• Friction of Rest: Friction is a force that opposes motion or tendency of motion between surfaces in contact. While friction can prevent an object from moving, it is a force, not the inherent property of resisting change in the state of rest.
• Flowability at Rest: Flowability relates to the ease with which a substance (usually a fluid) can flow. This term is irrelevant to the tendency of a solid object to remain stationary.
• Inertia of Rest: This option accurately describes the property. It specifically refers to the inertia of an object when it is in a state of rest – its tendency to remain at rest.
• Viscosity at Rest: Viscosity measures a fluid's resistance to gradual deformation by shear stress or tensile stress. It relates to the internal friction within a fluid and is not applicable here.

Conclusion on Inertia:

Therefore, the property described in the question is specifically inertia of rest. It highlights that objects prefer to maintain their current state, whether it's being at rest or in uniform motion. Applying an external force is necessary to overcome this inertia and change the object's state.