Around us, we see many examples of objects moving with constant acceleration where the rate of change of velocity is the same throughout the motion. For example, a ball falling under gravity has constant acceleration if the effects of air are neglected. The motion of objects with constant acceleration is approximated by kinematic equations, also known as equations of motion. These equations include variables like displacement, velocity, acceleration, and time. Recall that acceleration is the change of velocity with time. Now suppose, an object starts moving at time t1 equal to zero seconds with an initial velocity v0x, and after some time t2 equal to t seconds has a final velocity vx. After substituting these variables, the product of acceleration and time corresponds to the total change in velocity over time t. Thus, the x velocity at any time t is given by the sum of initial velocity and the change in x velocity. This expression for vx is the first fundamental kinematic equation.