Physics

A  unit of area often used in measuring land areas is the hectare, defined as $10^{4}m^{2}$. AN open pit coal mine consumes $75$ hectare of land, down to a depth of $26\ m$, each year. What volume of earth, in cubic kilometers, is removed in this time?

SOLUTION
1 hectare =$10^4 m^2$

Area of pit, A = 75 hectare

convert hectare into m^2

A = $75 \times10^4 m^2$

depth, d = 26 m

Volume of earth removed is V.

V = area of pit x depth

V = A x d

V = $75 \times 10^4 \times 26 = 1950 \times 10^4 m^3$

Convert cubic metre into cubic km

$1 m = 10^-3 km$

$1 m^3 = 10^-9 km^3$

So, You're just one step away

Subjective Medium Published on 18th 08, 2020
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