What term describes the change in an object's momentum when a force is applied over a period of time?

• A. Momentum
• B. Impulse
• C. Energy
• D. Work

Answer: (B)

When a force acts on an object for a period of time, it changes the object's momentum. Momentum is p = m v, so a force F applied for a time Δt changes the momentum by Δp. This change in momentum is defined as impulse, J, where J = Δp = F Δt. The impulse-momentum relationship shows that the effect of a force over time is precisely to alter the momentum.

Why this is the best term: impulse captures the duration and strength of the force together, exactly describing how momentum changes. Momentum itself describes the quantity before or after the interaction, energy is related to the ability to do work and is tied to speed and mass through kinetic energy, and work is the transfer of energy via displacement. None of those directly quantify the momentum change caused by a force over time the way impulse does.