WAEC Physics 2019 Paper

Concept:The gravitational force between two masses is given by Newton's law of universal gravitation.Explanation:Given that $m_1 = 3.0\, \mathrm{kg}$, $m_2 = 2.0\, \mathrm{kg}$, and distance $d = 50\, \mathrm{cm}$.Since the value of $G$ is in SI units, convert the distance to metres:$$d = 50\, \mathrm{cm} = 0.50\, \mathrm{m}$$Use the gravitational force formula:$$F = \frac{G\, m_1\, m_2}{d^2}$$Substitute the given values:$$F = \frac{(6.67 \times 10^{-11})(3.0)(2.0)}{(0.50)^2}$$Simplify the numerator:$$F = \frac{4.002 \times 10^{-10}}{0.25}$$$$F = 1.6 \times 10^{-9}\, \mathrm{N}$$Answer: The force of attraction between the two bodies is $1.6 \times 10^{-9}\, \mathrm{N}$. Hence, the correct option is A.