What Are SUVAT Equations?
When objects move with constant (uniform) acceleration, we can describe their motion using a set of equations known as the SUVAT equations. These equations connect five key variables that describe motion in a straight line.
The name SUVAT comes from the five variables themselves:
- s — displacement (metres, m)
- u — initial velocity (metres per second, m/s)
- v — final velocity (metres per second, m/s)
- a — acceleration (metres per second squared, m/s²)
- t — time (seconds, s)
A constant rate of change of velocity. The acceleration does not change over time. SUVAT equations are only valid when acceleration is constant.
SUVAT equations only work when acceleration is constant. If acceleration is changing (e.g. a car braking unevenly), you cannot use these equations directly.
Think of SUVAT as a toolkit for motion problems. If you know three of the five variables, you can always find the other two — just like solving a puzzle where three clues are always enough to reveal the full picture.
The Five SUVAT Variables in Detail
The straight-line distance from start to finish, including direction. Measured in metres (m). Different from distance — displacement is a vector quantity.
The velocity of the object at the very beginning of the time interval being studied. Measured in m/s.
The velocity of the object at the end of the time interval. Measured in m/s.
The rate of change of velocity. Measured in m/s². Can be positive (speeding up) or negative (slowing down — sometimes called deceleration).
The duration of the motion being studied. Measured in seconds (s).
Students often confuse distance and displacement. Displacement is a vector — it has both magnitude and direction. If a car travels 100 m forward and then 100 m back, the distance is 200 m but the displacement is 0 m. SUVAT equations use displacement, not distance.
When setting up a SUVAT problem, always write out all five letters (s, u, v, a, t) and fill in what you know before choosing which equation to use. This habit prevents errors and makes your working clear.
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