What Is the Gravitational Force Between Two Rocks in Space?

[BrainMan]

Homework Statement

Two identical rocks of mass 2 kg drift through space far from any planet or star. If they pass one another at a separation of 30 cm, what is the magnitude of the gravitational force of one rock on the other at this instant.

Homework Equations

F = G (m1m2/r²)

The Attempt at a Solution

(4/.3²)(6.673 x 10^-11) = F
(4/.09)(6.673 x 10^-11 = F
44.444444444444(6.673 x 10^-11 = F
F = 3.804 x 10^-8 N
the actual answer is F = 2.96 x 10³ N

 

[gneill]

Homework Statement

Two identical rocks of mass 2 kg drift through space far from any planet or star. If they pass one another at a separation of 30 cm, what is the magnitude of the gravitational force of one rock on the other at this instant.

Homework Equations

F = G (m1m2/r²)

The Attempt at a Solution

(4/.3²)(6.673 x 10^-11) = F
(4/.09)(6.673 x 10^-11 = F
44.444444444444(6.673 x 10^-11 = F
F = 3.804 x 10^-8 N
the actual answer is F = 2.96 x 10³ N

The "actual answer" is not correct, but it is the order of magnitude that is wrong not the mantissa of the number. Perhaps you misquoted the power of ten?

Regarding your solution attempt, your formula is fine but your math is not right. Recheck your calculation.

 

[BrainMan]

The "actual answer" is not correct, but it is the order of magnitude that is wrong not the mantissa of the number. Perhaps you misquoted the power of ten?

Regarding your solution attempt, your formula is fine but your math is not right. Recheck your calculation.

OK I see my mistake and the answer I put was a typo it is actually 2.96 x 10^-9 N