The expression for an object's acceleration in terms of its mass and velocity is called Newton's second law of motion. According to Newton's second law, the acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass. Mathematically, the expression is written as:
acceleration = force / mass
In terms of units, the SI (International System of Units) unit for acceleration is meters per second squared (m/s²). This means that acceleration is measured as the change in velocity per unit time.