Question
Thu September 15, 2011 By:

How far should a man go from the centre of the earth such that his weight is 1/4th that on the earth? Radius of Earth = 6400 km. [4 marks]

Expert Reply
Fri September 16, 2011

We know :

F= (GMm)/R2

Weight of the body= force exerted by the body= mg=F1……..(i)

G=gravitational constant

R=radius of the earth

M= mass of the body

If the body weighs ¼ of the weight  that on the earth ,then its distance from the center of the earth be R2.

F2=(1/4)F1……..(ii)

Dividing (ii) by(i)

(1/4)mg/mg=R12/R22

1/4= R12/R22

½= R1/R2

Given R1 =6400km

R2 =6400x2=12800km

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