# An object weighs 80 N on earth surface...?

The same object will weigh 20 N at an height from the surface of the earth?

a)R/4

b)2R

c)R/2

d)R

Please explain how???????? :(

### 3 Answers

- Anonymous6 years agoBest Answer
mass remains same every where

so mg=80

m=8.16 kg

when the object weigh 20 N

mg'=20

g'=20/8.16=2.451 m/s^2

now

F=GMm/r^2 [at surface]

mg =GMm/r^2

g=GM/r^2

F'=GMm/(r+h)^2 [at height h]

mg'=GMm/(r+h)^2

g'=GM/(r+h)^2

g'/g=r^2/(r+h)^2

2.451/9.8=(6400/(6400+h))^2

0.25=(6400/(6400+h))^2

6400/6400+h=0.5

6400=3200+0.5h

h=6400 km=r

so the answer is d

- SteveLv 76 years ago
Weight is inversely proportional to the square of the distance R from the center of the earth.

Ergo, if H = R → R' = 2R, g' = gR²/(2R)² = 0.25g

80*0.25 = 20

(d)

- 3 years ago
3.seventy 5 w=ma here, w1,w2 is weight of merchandise in earth and mars a1,a2 is acceleration in earth and mars mass would be comparable w1=m(a1) 350=m(9.5) =>m=35.seventy one w2=m(a2) 134=35.seventy one(a2) =>a2=3.seventy 5 subsequently C.3.seventy 5 is actual answer