Uniform linear motion or uniform rectilinear motion is the simplest motion that has the constant velocity. Some common problem of rectilinear motion: encounter, pursuit, the train passes through a bridge or a tunnel.

When the acceleration is constant and its direction is parallel to the initial velocity, the object moves along a straight line with uniform acceleration. It is a special example of accelerated motion.

Free fall is a special case of uniformly accelerated linear motion. The object starts moving from rest only due to gravity, and air resistance and buoyancy are neglected.

Galileo's experiment with a ball rolling down an inclined plane proved Aristotle's theory wrong. All objects, regardless of their weight, fall equally fast.