Concept Library / Kinematics

Constant Velocity Equation

The constant velocity equation predicts position during uniform motion:

s = s_{i} + v t

Full explanation

The constant velocity equation predicts position during uniform motion:

s = s_{i} + v t

The equation says:

final position = initial position + displacement during the time interval.

The displacement during the interval is $v t$ , but this only works when $v$ is constant over that interval.

Formula / representation

s = s_{i} + v t

where:

Graph representation:

Units

equation combines

m

s

, and

m s^{- 1}

Common misconceptions

Using $s = s_{i} + v t$ when velocity is changing.
Treating $s$ as distance travelled rather than position.
Forgetting that negative velocity decreases position.
Setting two position expressions equal without checking that both use the same origin and clock.

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