The Relationship Between Distance, Speed, and Time

What is uniform rectilinear motion?

A motion is uniform rectilinear motion (URM) when two conditions are met at the same time:

• the trajectory is a straight line (rectilinear)
• the speed remains constant over time (uniform)

An object in URM therefore covers equal distances in equal time intervals.

The fundamental formula

The relationship between distance (d), speed (v), and time (t) can be written in three ways depending on what you are looking for:

v = d / t d = v * t t = d / v

Concrete example

A train travels in a straight line at a constant speed of 40 m/s for 5 minutes, i.e. 300 s. What distance has it covered?

d = v * t = 40 * 300 = 12000 m = 12 km

Summary table

I am looking for	Formula	Consistent units
Speed	v = d/t	m/s (with d in m and t in s)
Distance	d = v*t	m
Time	t = d/v	s

Common pitfall to avoid

Before using a formula, always check that all quantities are expressed in the same units (meters and seconds, or kilometers and hours). Mixing kilometers with seconds is a very common mistake that completely distorts the result.