Gravity Physics Example 5

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Example 5

medium
What gravitational force exists between two 5 kg5 \text{ kg} masses whose centers are 2 m2 \text{ m} apart? Use G=6.674×10−11 N m2/kg2G = 6.674 \times 10^{-11} \text{ N m}^2/\text{kg}^2.

Solution

  1. 1
    Use Newton's law of gravitation: F=Gm1m2r2F = \frac{Gm_1m_2}{r^2}
  2. 2
    Substitute the values: F=(6.674×10−11)(5)(5)22=6.674×10−11×254F = \frac{(6.674 \times 10^{-11})(5)(5)}{2^2} = \frac{6.674 \times 10^{-11} \times 25}{4}
  3. 3
    Compute: F=4.17×10−10 NF = 4.17 \times 10^{-10} \text{ N}

Answer

F≈4.17×10−10 NF \approx 4.17 \times 10^{-10} \text{ N}
Gravity acts between all masses, but for everyday objects the force is extremely small because GG is tiny. Large masses or small separations are needed for noticeable effects.

About Gravity

The universal attractive force between any two objects with mass, decreasing with the square of distance.

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