Kinematics · 24 min
The Equations of Motion (SUVAT)
Five variables, four equations, and you never need all five at once.
Why should I care?
A stone is dropped and hits the ground 2.2 s later. How could you find its speed on impact without ever measuring it directly?
This is exactly what SUVAT equations are for — connecting displacement, initial velocity, final velocity, acceleration, and time so that knowing three lets you solve for the other two.
Explore
Watch the curve bend
Adjust acceleration and watch the position-time graph curve rather than stay straight — constant acceleration always produces a parabola in position, not a straight line.
The idea
The five SUVAT variables
s = displacement, u = initial velocity, v = final velocity, a = acceleration, t = time. These four equations link them, and each equation deliberately leaves one variable out — pick the one that skips the value you don't have.
True or false?
SUVAT equations work for any motion, including changing acceleration.
Worked example
Worked example
A stone is dropped from rest and falls for 2.2 s. Find its velocity on impact. (g = 9.8 m/s²)
- 1
List knowns: u = 0, a = 9.8 m/s², t = 2.2 s. Unknown: v.
Your turn
Which SUVAT equation should you use if you know u, a, and s, and want v — but don't know t?