Uniform linear motion or uniform rectilinear motion is the simplest motion that has the constant velocity. The displacement-time graph of uniform rectilinaer motion is a linear function and the velocity-time graph is a horizontal straight line. Since there is no change in velocity, the acceleration is zero.

## Encounter

Two cars are S kilometers apart, with velocities of magnitude v1 and v2, in opposite directions.

$t=\frac{s}{\mathrm{v\u2081\; +\; v\u2082}}$

## Pursuit

The faster car chases the slower car. The two cars are S kilometers apart, with velocities of magnitude is v1 and v2, in the same direction, and v1>v2.

$t=\frac{s}{\mathrm{v\u2081\; -\; v\u2082}}$

## The train passes through a bridge or a tunnel.

The s₁ meter train passes over the s₂ meter bridge at speed v. It starts when the locomotive enters the bridge and ends when the rear of the train leaves the bridge. The train displacement is s₁ + s₂.

$t=\frac{\mathrm{s\u2081\; +\; s\u2082}}{v}$