Which statement correctly defines momentum?

• A. Momentum is the force of motion
• B. Momentum is the energy of motion
• C. Momentum is the rate of change of velocity
• D. Momentum is mass times velocity

Answer: (D)

Momentum is the quantity of motion an object has, defined as the product of its mass and velocity. This makes momentum a vector, having both magnitude and direction—the direction is the same as the object's velocity, and its magnitude is m times the speed. The units are kilograms times meters per second (kg·m/s).

This concept differs from other ideas: kinetic energy is 1/2 m v^2, which grows with the square of speed, while acceleration is the rate of change of velocity. Momentum, defined as mass times velocity, explains why it’s conserved in isolated systems and why a heavy object moving slowly can have the same momentum as a lighter object moving faster.

Therefore, momentum being mass times velocity aligns with the defining quantity for momentum.