What Is the Gravitational Force Between Two Rocks in Space?

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SUMMARY

The gravitational force between two identical rocks, each with a mass of 2 kg and separated by 30 cm in space, is calculated using the formula F = G (m1m2/r²). The correct gravitational force is F = 2.96 x 10^-9 N, which was initially miscalculated as F = 2.96 x 10^3 N due to an error in the order of magnitude. The gravitational constant G is 6.673 x 10^-11 N(m/kg)², and the calculations must accurately reflect the squared distance in the denominator.

PREREQUISITES
  • Understanding of Newton's Law of Universal Gravitation
  • Familiarity with the gravitational constant (G = 6.673 x 10^-11 N(m/kg)²)
  • Ability to perform calculations involving powers of ten
  • Knowledge of basic algebra for manipulating equations
NEXT STEPS
  • Review Newton's Law of Universal Gravitation in detail
  • Practice calculations involving gravitational force with varying masses and distances
  • Learn about dimensional analysis to verify units in physics equations
  • Explore common mistakes in scientific notation and how to avoid them
USEFUL FOR

Students studying physics, educators teaching gravitational concepts, and anyone interested in understanding the calculations behind gravitational forces in space.

BrainMan
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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
 
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BrainMan said:

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.
 
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gneill said:
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
 

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