Question

The diameter of a metallic ball is 4.2cm. What is the mass of the ball, if the density of the metal is 8.9g/cm cube

Answer 1

Given that the diameter of ball = 4.2cm.

Then the radius of the ball will be r = d/2 =  4.2/2 = 2.1cm.

We know that volume = 4/3 pir^3

                                      = 4/3 * 22/7 * (2.1)^3

                                      = 4/3 * 22/7 * 2.1 * 2.1 * 2.1

                                      = 38.808.


Given the density of the metal = 8.9g/cm^3.

We know that density = mass/volume.

Then the mass = volume * density

                          = (38.808 * 8.9)

                          = 345.3.


Therefore the mass of the ball = 345.3g.


Hope this helps!                        

Answer 2

Diameter = 4.2cm
Therefore Radius = 2.1cm

Volume= 4/3×pi×r^3

= 4/3 × 22/7 × 2.1 × 2.1 × 2.1

=38.808 cm^3

Given Density= 8.9 g/cm^3

We know; D= Mass/Volume
Or;
Mass = Volume × density

=38.808 × 8.9

=345.3 g

Therefore mass of the ball = 345.3 g