Question

when a cricket ball is thrown vertically upwards it reaches a maximum height of 5 metre what is initial speed of the ball

Answer 1

Dear student,

From the equation $v^2-u^2=2as$.
Where a= -9.8m/s² ​the gravity is acting as negative acceleration so it takes negative sign ,s= 5 m,u is the initial velocity and v is final velocity and is zero because the ball stops at peak height
$$\begin{gathered} -u^2=2\times -9.8\times 5 \\ {u}^2=98 \\ u=9.8m/s \end{gathered}$$

Regards.