The property of a body to remain at rest or to continue in uniform motion in a straight line is called

Step 1: Analyze the question The question asks for the name of the property of a body that makes it keep its state of rest, or keep moving uniformly in a straight line, unless an external force acts on it.

Step 2: Explain the concept This is Newton's First Law of Motion, also called the Law of Inertia. It states that a body remains at rest, or continues in uniform motion in a straight line, unless acted upon by an external force. The property of resisting any change in this state is called inertia.

Step 3: Check each option

• A. Momentum: This is mass × velocity (p = mv). It measures the quantity of motion a body has, not its resistance to change.
• B. Inertia: This is the tendency of a body to stay at rest or in uniform motion in a straight line. It matches the definition exactly.
• C. Impulse: This is force × time (Ft), which equals the change in momentum. It is not a property of the body itself.
• D. Energy: This is the capacity to do work. It is unrelated to the definition.

Step 4: Answer The correct option is B. Inertia.

Real-life example: When a bus suddenly brakes, passengers lurch forward. Their bodies tend to keep moving in a straight line at the same speed, and that is inertia at work.

Exam tip: Remember that mass is the measure of inertia. A heavier body has more inertia, so it is harder to start or stop. If a question uses the words "remain at rest" or "continue in uniform motion," think inertia and Newton's First Law.