Which of the following conclusion(s) can be drawn from Newton’s second law of motion? Force is proportional to…

Step 1: Analyze the question We need to decide which statements follow from Newton's second law, which says that force is proportional to something.

Step 2: Recall the concept Newton's second law states that the rate of change of momentum of a body is directly proportional to the applied force, and the change takes place in the direction of the force.

F ∝ (mv − mu)/t

For constant mass, this becomes:

F ∝ m(v − u)/t = ma

So F = kma, and in SI units k = 1, giving F = ma.

Step 3: Check each statement

• I. Product of mass and acceleration: Yes. F = ma follows directly from the law.
• II. Product of mass and velocity: This is momentum. The law says force is proportional to the rate of change of momentum, not to momentum itself. A body moving at constant velocity has momentum but no net force, so this is false.
• III. Impulse: Impulse = Ft, so force is proportional to impulse only if time is held constant. Impulse is the change in momentum (Ft = mv − mu). Force is proportional to impulse divided by time, so force is not simply proportional to impulse. This is not a direct conclusion of the law.

Step 4: Answer Only statement I is a direct conclusion from Newton's second law.

Answer: A. I only

Exam tip: Remember that force is proportional to the rate of change of momentum (Δp/t), not to momentum itself. If an option says "force ∝ momentum" or "force ∝ mv", it is a trap.