Constant-acceleration equations
Three formulas that link position, velocity, acceleration and time when acceleration does not change.
Last updated
Analogy
A toolkit for any motion with a steady push, like a car braking evenly.
Example
v0 = 20 m/s, v = 0, a = -5 m/s^20 = 20^2 + 2(-5)dd = 400 / 10 = 40 m
In practice
Use v squared = v0 squared + 2 a d when time is not given.
Practice
Flashcards
- Which equation links v, v0, a and displacement without time?v^2 = v0^2 + 2 a d.
Questions people ask
When can I not use the constant-acceleration equations?
They only work when acceleration stays the same the whole time. A car that keeps changing how hard it accelerates breaks the rule. A falling stone near the ground works well. A skydiver slowed by growing air drag does not, so these formulas fail there.
How do I choose which kinematic equation to use?
List what you know and what you want. Each equation leaves out one of the five quantities: displacement, initial velocity, final velocity, acceleration and time. Pick the one that skips the quantity you neither have nor need. That keeps the algebra short and the answer clean.