Question

Find the percentage decrease in the weight of the body when taken to a depth of $32$ km below the surface of earth. Radius of the earth is $6400$km.

• A. 0.7
• B. 0.5
• C. 1.2
• D. cant say
  

Answer 1

The correct option is B 0.5

Here, $d=32$km; $R=6400$km
Weight of body at depth d is $=m{g}^{\prime }=mg(1-\frac{d}{R})$
$\%$ decrease in weight $=\frac{mg-m{g}^{\prime }}{mg}$
$=\frac{d}{R}\times 100=\frac{32}{6400}\times 100=0.5\%$.