Question

A shotput is a metallic sphere of radius 4.9 cm. If the density of the metal is 7.8 g. per cm${}^3$, find the mass of the shotput.

Answer 1

Since the shot-put is a solid sphere made of metal and its mass is equal to the product of its volume and density, we need to find the volume of the sphere.

Now, volume of the sphere $=\frac{4}{3}\pi r^3$

$=\frac{4}{3}\times \frac{22}{7}\times 4.9\times 4.9\times 4.9c{m}^3$

$=493c{m}^3$ (nearly)

Further, mass of 1 cm${}^3$ of metal is $7.8g$

Therefore, mass of the shot-put $=7.8\times 493g$

$=3845.44g=3.85kg$ (nearly)