Given: gd = 90% of g i.e., `"g"_"d"/"g"` = 0.9, To find: Distance below the Earth’s surface (d) Formula: gd = `"g"(1 - "d"/"R")` Calculation: From formula, `"g"_"d"/"g" = (1 - "d"/"R")` ∴ `"d"/"R" = 1 - "g"_"d"/"g"` ∴ d = R`(1 - "g"_"d"/"g")` = 6.4 × 106 × 0.1 = 640 × 103 m = 640 km At distance 640 km below the surface of the Earth, value of acceleration due to gravity decreases by 10%. |