KinexiaLEARN PHYSICS

SUVAT Velocity — Sprinter Accelerating from Rest (Worked Example)

Easy
Problem

A sprinter explodes out of the starting blocks from rest and accelerates uniformly at 2.5 m/s² for 4.0 s during the drive phase. What is her velocity at the end of these 4.0 seconds?

Given

  • u = 0 m/s (starts from rest)

  • a = 2.5 m/s²

  • t = 4.0 s

Find

The final velocity v.

Principle

For constant acceleration, velocity increases linearly with time. The SUVAT equation v = u + at adds the velocity gained (a × t) to the starting velocity.

Formula

Solution

  1. Write the equation: v=u+atv = u + at

  2. Substitute the values: v=0+(2.5)(4.0)v = 0 + (2.5)(4.0)

  3. Multiply: v=10 m/sv = 10\ \mathrm{m/s}

10 m/s

Unit check

m/s² × s = m/s. The units match velocity — dimensionally consistent.

What this means physically

After 4 seconds the sprinter moves at 10 m/s (36 km/h). Elite sprinters peak near 12 m/s, so this is a realistic drive-phase speed before top-end running begins.

Common mistake

Forgetting to add the initial velocity u. Here u = 0 so it hides, but in most problems u is nonzero and skipping it gives the velocity gained, not the final velocity.