Question

how gravitational acceleration varies with height .

Answer 1

Gravitational acceleration depends on height as

$\displaystyle g_h = g_0 (\frac{R_e}{R_e+h})^2$ ,

where $g_h$ is gravitational acceleration at a certain height, $g_0 = 9.80665$  m/s2 is standard gravitational acceleration, $R_e$ is the Earth's radius, $h$ is height.

As we see from the formula, gravitational acceleration decreases with height.

So when $h=0$ m, that means that you're at the Earth ocean-level surface, then $g_h = g_0$. In mountains $g_h$ will be just a bit smaller, the difference is less than 1 %. Only going to the height of ionosphere and low orbit satellites ($h \leq 2000$ km) will make you feel a big difference.