Question

A hole is drilled half way to the centre of the earth. A body weighs 300 N on the surface of the earth. How much will, it weigh at the bottom of the hole?

Options

• 200 N

• 250 N

• 120 N

• 150 N

Answer 1

150 N

Explanation:

Given, distance of bottom of hole from the surface of earth (d) = half the radius of earth = `"R"_"e"/2`.

If g be the value of gravitational acceleration on the surface of earth, then weight of body

mg = 300 N

If g' be the gravitational acceleration at the bottom of hole, then

g' = `"g"(1 - "d"/"R"_"e")`

`= "g"(1 - ("R"_"e"/2)/"R"_"e")`

`=> "g'" = "g"/2`

∴ Weight of the body on the bottom of hole,

mg' = `"mg"/2 = 300/2` = 150 N