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JAMB Physics 2015 Paper

Question : 15

Total: 66

10^{24}

10^{27}

10^{20}

meters

Solution:

Concept:

Newton’s law of universal gravitation gives the force between two masses separated by a distance.

Explanation:

Use the formula

F = \frac{G m_1 m_2}{r^2}

Given:

m_1 = 10^{24}\ \mathrm{kg}

m_2 = 10^{27}\ \mathrm{kg}

r = 10^{20}\ \mathrm{m}

The gravitational constant is

G = 6.67 \times 10^{-11}\ \mathrm{N\,m^2\,kg^{-2}}

Substitute the values into the formula:

F = \frac{(6.67 \times 10^{-11})(10^{24})(10^{27})}{(10^{20})^2}

Simplify the powers of ten:

10^{-11 + 24 + 27} = 10^{40}

The denominator is

10^{40}

, so they cancel.

F = 6.67 \times \frac{10^{40}}{10^{40}} = 6.67\ \mathrm{N}

Answer:

The gravitational force of attraction is

6.67\ \mathrm{N}

, which is option A.

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