Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.

• A. Acceleration
• B. Velocity
• C. Inertia
• D. Momentum

Answer: (A)

Acceleration is the rate at which velocity changes with time, and it is produced by a force acting to overcome inertia. Inertia is the resistance to changes in motion, so applying a force changes how fast (or in what direction) an object is moving, and that change is what we call acceleration. According to F = m a, the acceleration depends on the applied force and the object's mass—the same force produces a larger acceleration on a lighter object and a smaller one on a heavier object. Velocity, by contrast, is simply how fast and in what direction the object is moving at a given moment, not how quickly that motion is changing. Inertia is the tendency to keep doing what it’s already doing, and momentum is the product of mass and velocity, describing the motion itself rather than its rate of change. So the force involved in changing motion, i.e., overcoming inertia, is acceleration.