Question

CU ULU
At what height above the surface of earth the value
of "g" decreases by 2%? (radius of the earth is
6400 km]
(1) 32 km
(2) 64 km
(3) 128 km
(4) 1600 km​

Answer 1

Answer:

C

Explanation:

Answer 2

Dear student,

Given :-

• acceleration due to gravity decreases by 2%

To find :-

• height above the earth surface the mentioned decrease occurs

Solution :-

We know for a small height above the ground between 20 km to 500 km, for the acceleration due to gravity, we use the formula derived with the help of binomial approximation. That is as;

     g = g' ( 1 - 2h / R)

Putting the given value in the above formula and shifting positions we get;

g = g' - g'2h / R

100 × Δg/g = - 2h/ R × 100

- 2 = - 2h/ 6400 × 100

h = 128/ 2

h = 64 km

Hence, the height above the ground is 64 km.