The kinematic equations of motion are useful to solve problems involving one-dimensional motion of objects under constant acceleration. Consider a couple driving to a nearby coffee shop. They start the car and apply a constant acceleration of 2 meters per second squared. What will be the car's velocity after 20 seconds and the distance covered by it in that time? The choice of the equation to solve the problem depends on the known quantities and the unknown quantities. Here, the known quantities are constant acceleration, time, the initial position, and the initial velocity, as the car was at rest. The unknown quantities are the velocity and distance covered after 20 seconds, which can be calculated using the first and second kinematic equations. Substituting known values in the first kinematic equation gives the velocity of the car, which equals 40 meters per second. Then, substituting the known values in the second kinematic equation, simplifying and solving it gives the distance covered by the car equal to 400 meters.