How is Force defined?

• A. distance/time
• B. mass x acceleration
• C. velocity x acceleration
• D. force x velocity

Answer: (B)

Force is defined by Newton's second law: the net force on an object equals its mass times its acceleration. In symbols, F = m a. This means force is what causes an object's mass to accelerate, and for a given mass, doubling the net force doubles the acceleration. The units line up too: kilograms times meters per second squared give newtons, the standard unit of force.

Distance over time describes speed (or velocity with direction), not force. Velocity multiplied by acceleration isn’t a standard quantity for force, and force multiplied by velocity describes power, which is the rate of doing work, not the force itself.