1)

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


A) 200 N

B) 250 N

C) 120 N

D) 150 N

Answer:

Option D

Explanation:

 Given, distance of bottom of hole from the surface of earth (d)= half the radius of earth =  $\frac{R_{e}}{2}$

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

   mg= 300N

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

$g'=g\left(1-\frac{d}{R_{e}}\right)=g\left(1-\frac{\frac{R_{e}}{2}}{R_{e}}\right)\Rightarrow g'=\frac{g}{2}$

$\therefore$     Weight of the body on the bottom of hole,

$mg'=\frac{mg}{2}=\frac{300}{2}=150 N$