Newton's Second Law Calculator

Newton's second law connects net force, mass, and acceleration through the compact equation F equals m times a. It states that an object's acceleration is directly proportional to the net external force and inversely proportional to its mass. The acceleration points in the same direction as the net force. This relationship is the foundation of classical dynamics and is used to predict motion in vehicles, machinery, structures, sports, laboratory experiments, and countless everyday situations. Force is measured in newtons in the SI system. One newton is the force required to accelerate one kilogram by one metre per second every second. Mass is measured in kilograms and represents inertia, or resistance to acceleration. Acceleration is measured in metres per second squared and describes how rapidly velocity changes. When two quantities are known, the equation can be rearranged: force equals mass times acceleration, mass equals force divided by acceleration, and acceleration equals force divided by mass. The force in this law is net force, not necessarily one individual push or pull. All external force vectors must first be combined with signs and directions. A car engine may provide a forward driving force while drag and rolling resistance act backward; only their difference accelerates the car. Likewise, an object resting on a table has downward weight and an upward normal force that balance, producing zero vertical acceleration. A zero net force does not require zero velocity; it means velocity remains constant. This calculator uses signed numerical values, so a negative force can represent the direction opposite the chosen positive axis and can produce negative acceleration. Mass should remain positive. The model assumes constant mass and an inertial reference frame. Variable-mass systems such as rockets require momentum analysis, while speeds near the speed of light require relativistic mechanics. Rotating rigid bodies also require the angular counterpart involving torque and moment of inertia. For ordinary translational motion at everyday speeds, however, Newton's second law gives a clear and highly accurate link between cause and motion. Always use consistent SI units or convert values before calculating.