An athlete starts running from rest. He accelerates uniformly and completes 200 metre race in 10 seconds. Find his acceleration.

Solution,
Given
An athlete starts running from rest, i.e., initial velocity, u = 0 m/s
He accelerates uniformly. Assuming this acceleration be a.
He completes a distance,  d = 200 m in time t = 10s.
Thus,
Using the kinematic relation for motion under uniform acceleration:
$$\begin{gathered} d=ut+\frac{1}{2}a{t}^2 \\ 200=\frac{1}{2}a{t}^2 \\ 200=\frac{1}{2}a\times {10}^2 \\ a=\frac{200\times 2}{100}=4m/s^2 \end{gathered}$$