Question

Distance between earth and moon is 3·8 × 105
km and the mass of earth is 81 times
the mass of the moon. Find where the C.M. of earth moon system lies.

Answer 1

Answer:

3.8×10

7

m

Explanation:

Let at the point P the net gravitational force be zero.

Let,M=mass of the Earth

m=mass of the moon

m

′

=mass of the object

M=81cm (given)

(R−r)

2

Gmm

′

=

r

2

Gmm

′

=>

(R−r)

2

81

=

r

2

1

=>

{(3.8×10

5

)−r}

2

81

=

r

2

1

Solving,we get ,r=3.8×10

7

m