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WAEC Physics 2018 Paper

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Question : 31

Total: 50

Two objects P and Q of masses 100kg and 20kg respectively are 1.2m apart on a horizontal surface. Calculate the net gravitational force acting on Q.

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

$1.11 \times 10^{-7}\,\mathrm{N}$ towards P
$1.11 \times 10^{-7}\,\mathrm{N}$ towards Q
$9.26 \times 10^{-8}\,\mathrm{N}$ towards P
$9.26 \times 10^{-8}\,\mathrm{N}$ towards Q

Solution:

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

$m_1 = 100\,\mathrm{kg}$

$m_2 = 20\,\mathrm{kg};\ r = 1.2\,\mathrm{m}$

$G = 6.67 \times 10^{-11}$

$F = \frac{6.67 \times 10^{-11} \times 100 \times 20}{(1.2)^2} = 9.26 \times 10^{-8}$

The acceleration of each object is inversely proportional to the mass, the lighter object will move a bit faster, hence. the force will act in the direction of Q.

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