Question

According to Newton's first law of motion,

• A. Every body continues in its state of rest or uniform motion in a straight line unless acted upon by an external force.
• B. The rate of change of momentum is proportional to the impressed force and in the same direction
• C. To every action there is an equal and opposite reaction
• D. None of the above

Hint:

Inertia is directly proportional to the mass of an object. The more mass an object has, the more it resists changes to its state of motion.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Newton's First Law of Motion, often called the Law of Inertia, describes the behavior of objects when the net external force acting on them is zero.

Step 2: Detailed Explanation:
The law states that an object will not change its motion unless a force acts on it.
• If the object is at rest, it stays at rest.
• If the object is in motion, it stays in motion with the same speed and in the same direction. This resistance to change in the state of motion is known as inertia. Option (B) describes the second law, and option (C) describes the third law.

Step 3: Final Answer:
The statement in option (A) correctly defines Newton's first law of motion.

Answer 2

The question asks which statement correctly expresses Newton's first law of motion. Each of the three laws has a distinctive shape of statement, a purely qualitative description, a quantitative proportional relationship, or a paired-force statement, so we can identify the right option by matching the type of each statement to the type of each law.

1. Every body continues in its state of rest or uniform motion in a straight line unless acted upon by an external force: This is a purely qualitative statement about what happens (or does not happen) in the absence of a net force, with no formula or proportionality involved. That is exactly the character of the first law, also called the law of inertia.
2. The rate of change of momentum is proportional to the impressed force and in the same direction: This statement expresses a quantitative, proportional relationship between force and the resulting change in momentum. That proportional-relationship structure is the signature of the second law, not the first.
3. To every action there is an equal and opposite reaction: This is a paired-force statement, describing a mutual interaction between two bodies. That structure belongs to the third law.
4. None of the above: Since the first option's wording matches the qualitative, force-free description that defines the first law, this option is incorrect.

Matching statement types to law types leaves only the qualitative rest-or-uniform-motion description as the first law.

Therefore, the correct answer is every body continues in its state of rest or uniform motion in a straight line unless acted upon by an external force.