# 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 $\mathrm{cm}^{3}$ ?

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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 $345.3912\ g$.

Updated on 10-Oct-2022 13:46:39