Write the equation of total mechanical energy of a body having mass $m$ and stationary at height $H$.

(N/A) The total mechanical energy $(E)$ of a body is the sum of its kinetic energy $(K)$ and potential energy $(U)$.
$E = K + U$
For a body of mass $m$ at height $H$ that is stationary,its velocity $(v)$ is $0$.
Therefore,the kinetic energy $K = \frac{1}{2}mv^2 = \frac{1}{2}m(0)^2 = 0$.
The gravitational potential energy $U$ at height $H$ relative to the ground is given by $U = mgH$.
Thus,the total mechanical energy is $E = 0 + mgH = mgH$.