Find the weight of an object at a height of 6400 km above the
earth’s surface. The weight of the object

at
the surface of the earth is 20 N and the radius of the earth is 6,400 km.

Plz answr this fast i need the answer to this question today itself.....plz fast....

2

Answers

2014-09-28T21:45:06+05:30
F = GMm
         R² 
M is the mass of the Earth m is the mass of the object 
R is the radius of the earth =6400km(given)

When object is kept on surface.
W=F=GMm= 20 N
            R
²
 When object is lifted to a certain height=R' = R+h = 2R
 h = R = 6400 km
Now we have weight of  the object is

W' = F' =  GMm
                (2R)
² 
W' = (1/4).(GMm)
                    R
² 
=W
  4
Now the weight of the object will be
weight=20
             4
W=5N
2 4 2
2014-09-28T22:03:17+05:30
We know that  F=Gm₁m₂/d²
⇒20N=Gm₁m₂/R²..............(i)
given radius is 6400km=R
the body is at 6400 above the level of ground.
so total radius becomes 2R
⇒F=Gm₁m₂/(2R)²
   F=Gm₁m₂/4R²
   F=Gm₁m₂/R²*1/4
  F=20N*1/4...(from eqn (i))
  F=W=5N
3 4 3