JAMB 2024 Physics · Question 17

The gravitational force between two objects masses 10 ^ 24 kg and 10 ^ 27 kg is 6.67N. Calculate the distance…

Question

The gravitational force between two objects  masses 1024^{24}kg and 1027^{27}kg is 6.67N. Calculate the distance between them [ G = 6.6 x 10−11^{-11}Nm2^2kg−2^{-2} ]

  1. A.1.0 x 1020^{20}m
  2. B.2.0 x 10−20^{-20}m
  3. C.1.0 x 10−20^{-20}m
  4. D.2.0 x 1020^{20}m

Answer: A. 1.0 x 1020^{20}m

Explanation written with AI and checked against the answer key

Analysis

To solve this problem, we use Newton’s Law of Universal Gravitation, which states that the force (FF) between two masses is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Concept

The formula is:

F=G⋅m1⋅m2r2F = \frac{G \cdot m_1 \cdot m_2}{r^2}

Where:

  • FF = Gravitational force (6.67 N6.67 \, \text{N})
  • GG = Gravitational constant (6.67×10−11 Nm2kg−26.67 \times 10^{-11} \, \text{Nm}^2\text{kg}^{-2})
  • m1m_1 = Mass 1 (1024 kg10^{24} \, \text{kg})
  • m2m_2 = Mass 2 (1027 kg10^{27} \, \text{kg})
  • rr = Distance between the objects (what we need to find)
Step-by-Step Solution
  1. Rearrange the formula to solve for rr: $r2=G⋅m1⋅m2Fr^2 = \frac{G \cdot m_1 \cdot m_2}{F}$
  1. Substitute the given values into the equation: $r2=(6.67×10−11)×(1024)×(1027)6.67r^2 = \frac{(6.67 \times 10^{-11}) \times (10^{24}) \times (10^{27})}{6.67}$
  1. Simplify the calculation: • The 6.676.67 in the numerator and denominator cancel each other out: $r2=10−11×1024×1027r^2 = 10^{-11} \times 10^{24} \times 10^{27}$ • Use the law of indices (am×an=am+na^m \times a^n = a^{m+n}): $r2=10(−11+24+27)r^2 = 10^{(-11 + 24 + 27)}$ $r2=1040r^2 = 10^{40}$
  1. Find the square root to get rr: $r=1040r = \sqrt{10^{40}}$ $r=1020 mr = 10^{20} \, \text{m}$

This can be written as 1.0×1020 m1.0 \times 10^{20} \, \text{m}.

Conclusion

Comparing our result to the given options, we find that it matches option A.

Exam Tip: When dealing with powers of 10 in physics calculations, always handle the coefficients (the numbers in front) separately from the exponents. This prevents errors when moving decimals. Also, remember that 1040\sqrt{10^{40}} is simply 1040/2=102010^{40/2} = 10^{20}.

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