In a qualitative way, the tendency of an undisturbed object to remain at rest or to continue moving with the same velocity is called what?

Introduction / Context:
This question comes from Newton first law of motion and asks about a key concept in mechanics. The law describes how objects behave when no net external force acts on them. The qualitative term that captures the tendency of matter to resist changes in its state of motion is very important in understanding why seat belts are needed, why passengers lurch forward when a bus stops and many other everyday phenomena.

Given Data / Assumptions:

• The object in question is undisturbed, meaning no net external force is acting on it.
• We are told the object tends to stay at rest or continue moving at constant velocity.
• Options include force, acceleration, friction and inertia.
• We assume basic Newtonian mechanics applies.

Concept / Approach:
Newton first law states that a body continues in its state of rest or uniform motion in a straight line unless acted upon by a net external force. The property of matter that resists changes in its state of motion is called inertia. Heavier bodies usually show greater inertia and are more difficult to start or stop. Force is what changes motion, acceleration is the result of net force and friction is a specific kind of resistive force, not the general tendency to resist change. Therefore, the correct term for this tendency is inertia.

Step-by-Step Solution:
Step 1: State Newton first law in words: an object remains at rest or in uniform straight line motion unless a net external force acts on it. Step 2: Recognise that this behaviour reflects a built in resistance to changes in motion. Step 3: This resistance to change in the state of rest or uniform motion is given the name inertia. Step 4: Force is the external agency that can overcome inertia and change the motion, so it is not the tendency itself. Step 5: Acceleration is the change in velocity produced by a net force; it is an effect, not the tendency to resist change. Step 6: Friction is a specific force that always opposes motion or attempted motion; it is not the universal property of all matter. Step 7: Conclude that inertia is the correct term for the described tendency.

Verification / Alternative check:
Consider a heavy truck and a light car at rest. It is harder to start the truck moving because it has more mass and therefore more inertia. When both are moving at the same speed, it is also harder to stop the truck. Similarly, when a moving bus brakes suddenly, passengers tend to move forward due to their inertia, as their bodies try to maintain the previous state of motion. These examples confirm that inertia is the property that resists changes in motion, consistent with the definition in the question.

Why Other Options Are Wrong:
Force is what causes changes in motion according to Newton second law; it is not the resistance to change. Acceleration is the change in velocity per unit time and results from a net force, not the tendency to remain unchanged. Friction is a specific type of contact force that opposes relative motion between surfaces and is not a general property of matter.

Common Pitfalls:
Students sometimes confuse inertia with friction because both can oppose motion. However, friction is an external force between surfaces, whereas inertia is an inherent property of mass. In a frictionless environment, inertia still exists and objects continue moving in straight lines. To avoid confusion, remember that inertia is tied to mass, and Newton first law is often called the law of inertia to highlight this fundamental concept.

Final Answer:
The tendency of an undisturbed object to remain at rest or keep moving with constant velocity is called inertia.