Test Index

WAEC Physics 2018 Paper

© africaexams.com

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:

Concept:

Gravitational force between two masses is given by Newton's law of gravitation and is always attractive, pulling each mass toward the other.

Explanation:

The force on

Q

due to

P

is

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

.

Here,

m_1 = 100\,\mathrm{kg}

,

m_2 = 20\,\mathrm{kg}

, and

r = 1.2\,\mathrm{m}

.

Substitute:

F = \dfrac{6.67 \times 10^{-11} \times 100 \times 20}{(1.2)^2}

.

Calculate:

F = \dfrac{6.67 \times 10^{-11} \times 2000}{1.44} = 9.26 \times 10^{-8}\,\mathrm{N}

.

Since gravity is attractive,

Q

is pulled toward

P

.

Answer:

9.26 \times 10^{-8}\,\mathrm{N}

towards

P

.

Correct option: C.

© africaexams.com

Go to Question:

Prev Question

Next Question