What quantity is the product of an object's mass and its velocity?

• A. Momentum
• B. Impulse
• C. Kinetic Energy
• D. Inelastic Collision

Answer: (A)

Momentum is the product of an object's mass and its velocity. Since velocity includes direction, momentum is a vector that points in the same direction as the motion; reversing direction changes the momentum’s sign. Its units are kilogram meters per second (kg·m/s). Momentum tells us how hard it is to bring the object to a stop—the larger the momentum, the harder to stop.

In a system with no external forces, momentum is conserved during interactions like collisions, meaning the total momentum before equals the total momentum after.

Impulse is related but different: it’s the change in momentum caused by a force acting over a time interval, equal to the force times the contact time. Kinetic energy, on the other hand, is 1/2 m v^2 and is a separate quantity that can change independently of momentum. Inelastic collisions are a type of collision where kinetic energy isn’t conserved, though momentum is still conserved.

For example, a 2 kg object moving at 3 m/s has momentum 6 kg·m/s in the direction of motion.