A force acting upon a body causes it to accelerate in the direction of the force. Acceleration is directly proportional to the mass of the body being accelerated.

A force acting upon a body causes it to accelerate in the direction of the force. Acceleration is directly proportional to the mass of the body being accelerated.

• A. Newton's 1st law of motion
• B. Newton's 2nd law of motion
• C. Bernoulli's principle
• D. Doppler effect

Answer: (B)

Newton's second law explains how force, mass, and acceleration relate. It says that the acceleration a of a body is in the same direction as the net force F acting on it, and its magnitude is proportional to F and inversely proportional to the mass: a = F/m. So for a fixed force, heavier objects accelerate less, and for a fixed mass, increasing the force increases the acceleration. The statement in the prompt correctly notes that the acceleration follows the force in direction, and the best match is this law, though the usual relation is inverse to mass (not directly proportional to mass). Newton's first law is about inertia: without a net external force, motion remains unchanged. Bernoulli's principle deals with pressure and speed in fluids, and the Doppler effect concerns changes in frequency due to relative motion. None of those describe how force translates to acceleration through mass.

Newton's second law explains how force, mass, and acceleration relate. It says that the acceleration a of a body is in the same direction as the net force F acting on it, and its magnitude is proportional to F and inversely proportional to the mass: a = F/m. So for a fixed force, heavier objects accelerate less, and for a fixed mass, increasing the force increases the acceleration. The statement in the prompt correctly notes that the acceleration follows the force in direction, and the best match is this law, though the usual relation is inverse to mass (not directly proportional to mass).

Newton's first law is about inertia: without a net external force, motion remains unchanged. Bernoulli's principle deals with pressure and speed in fluids, and the Doppler effect concerns changes in frequency due to relative motion. None of those describe how force translates to acceleration through mass.