The diameter of a metallic ball is $ 4.2 \mathrm{~cm} $. What is the mass of the ball, if the density of the metal is $ 8.9 \mathrm{~g} $ per $ \mathrm{cm}^{3} $ ?
Given:
The diameter of a metallic ball is \( 4.2 \mathrm{~cm} \).
The density of the metal is \( 8.9 \mathrm{~g} \) per \( \mathrm{cm}^{3} \).
To do:
We have to find the mass of the ball.
Solution:
Diameter of the metallic ball $= 4.2\ cm$
This implies,
Radius of the metallic ball $r = \frac{4.2}{2}\ cm$
$= 2.1\ cm$
Volume of the metallic ball $=\frac{4}{3} \pi r^{3}$
$=\frac{4}{3} \times \frac{22}{7} \times(2.1)^{3}$
$=\frac{4}{3} \times \frac{22}{7} \times 2.1 \times 2.1 \times 2.1$
$=38.808 \mathrm{~cm}^{3}$
We know that,
$\text { Density } = \frac{\text { Mass }}{\text { Volume }}$
Mass $=$ Density $\times$ Volume
$=8.9\times38.808\ g$
$=345.3912\ g$
Therefore, the ,mass of the ball is $345.3912\ g$.
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