Practice

a = Δv/t Formula – How to Calculate Acceleration (Practice)

a = (v − u)/t — Average acceleration from change in velocity

Average acceleration is the change in velocity divided by time: a = (v − u)/t. Negative a usually means slowing down when forward is positive.

Guide — how to use this formula

1. 1. Convert speeds to m/s and time to seconds.
2. 2. Compute a = (v − u)/t (keep the sign).
3. 3. Or rearrange: v = u + at, t = (v − u)/a.
4. 4. With mass, net force is F = ma.

Derivation

Acceleration is the rate of change of velocity:

1. Definition for constant (average) a:
   a = \frac{\Delta v}{t} = \frac{v-u}{t}
2. Rearrangements used in SUVAT:
   v = u + at

Always subtract initial from final: (v − u), not (u − v).

Examples

Example: 0 to 20 m/s in 5 s

a = (20 − 0)/5 = 4 m/s².

Example: braking

25 → 5 m/s in 4 s → a = −5 m/s².

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